The effect of hypophysectomy on the uterine response to estradiol.

The Effect of Hypophysectomy on the Uterine Response to Estradiol JOHN L. KIRKLAND, RUSSELL M. GARDNER,* JUDY S. IRELAND, AND GEORGE M. STANCELf Department of Pharmacology and Department of Pediatrics, The University of Texas Medical School at Houston, Houston, Texas 77025 ABSTRACT. Following estradiol (E2) administration early increases (within 4 h) in uterine wet weight and the synthesis of 2-deoxyglucose-6-phosphate (2-DGP) from 2-deoxyglucose (2-DG) are similar in ovariectomized (OVX) and ovariectomizedhypophysectomized (OVX-HX) rats. Most late uterine responses occurring 24 h after hormone treatment, however, are greatly diminished in OVXHX animals relative to OVX animals. The diminished responses include increases in uterine wet weight, dry weight, RNA content, protein content and the incorporation of thymidine into uterine DNA. These late uterine responses are not diminished in OVXSham HX rats relative to OVX rats. The diminished

responses observed in OVX-HX rats are not due to a shift in the dose-response curve for E2, but result from a decrease in the magnitude of the maximum uterine response. These diminished responses are not due to alterations in the content, structure or binding affinity of uterine E2 receptors in OVX-HX rats relative to OVX rats. One late response, the synthesis of 2-DGP from 2-DG 24 h after E2 treatment, is not significantly diminished in OVX-HX rats. These results suggest that a pituitary factor(s) is directly or indirectly required for the complete uterine response to E2 to occur normally in OVX rats. (Endocrinology 101: 403, 1977)

T

HE OVERALL response of the rat uterus to estrogens is a complex process which seems to involve at least two major temporal phases, an early phase and a late phase (1-5). Specific responses occurring in the early phase are increases in uterine wet weight (3,6,7), glucose metabolism (7-9) and RNA polymerase activities (10-12) while late responses include increases in uterine dry weight (4-6), DNA synthesis (9,13), protein (10,14) and RNA content (10,14). It has been suggested that these late uterine responses represent true growth of the organ, while the early responses represent a preparation for this growth. The overall uterine response appears to be mediated by a series of interacReceived January 3, 1977. Supported by NIH Grant HD-08615. A preliminary' report of this investigation was presented at the Fall Meeting of the American Society for Pharmacology and Experimental Therapeutics, New Orleans, Louisiana, August 15-19, 1976 (The Pharmacologist 18: 250, 1976, Abstract 749). * Recipient of NIH Research Fellowship Award (Am 05246). t Recipient of NIH Research Career Development Award (I KO4 HD00099).

tions in which hormonal regulation may exist at multiple sites within uterine nuclei and at various times after hormone treatment (see 5 and 15 for recent reviews). In this investigation we have sought to determine if the overall endocrine status of the animal could differentially affect these early and late uterine responses to estrogens, since these responses are qualitatively distinct. As an initial approach to this question, we have compared various estrogenic responses of the uterus in ovariectomized (OVX) and ovariectomized-hypophysectomized (OVX-HX) rats. These studies indicate that early uterine responses are comparable in both.groups of animals, but that most late uterine responses are dramatically decreased in the OVX-HX animals. Materials and Methods Animals used in this study were purchased from Zivic-Miller Laboratories, Allison Park, Pennsylvania, which also performed all surgical procedures. Immature Sprague Dawley rats (50 g body weight) were either ovariectomized (OVX), ovariectomized-hypophysectomized (OVX-HX) or ovariectomized-sham hypophysectomized

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(OVX-Sham HX), and were maintained for 21 days after surgery prior to use. The OVX-HX rats were given normal rat chow ad libitum and drinking water containing 5% sucrose and the following components (numbers in parentheses represent mg/liter): NaCl (2030); KC1 (86); CaCl2 (36); MnCl2 (154); ZnCl2 (1.0); FeCl 3 (0.06); MgCl2 (0.125); tetracycline, American Cyanamid Polyotic Powder (400). OVX and OVXSham HX animals were given rat chow and water ad libitum. Immediately prior to use the mean body weights of the OVX animals ranged from 138 to 170 g in various experiments, and these values were not significantly different from the OVX-Sham HX groups. Mean body weights of the OVX-HX groups ranged from 65 to 85 g. Either 4 or 24 h prior to sacrifice animals were injected ip with the doses of 17/3-estradiol (Schwarz/Mann) indicated in the text for individual experiments or the vehicle alone (control groups). Estradiol was routinely administered in 0.5 ml of 95% saline—5% EtOH, except in the dose-response studies where 0.5 ml of 50% saline—50% propylene glycol was used. Animals were sacrificed by decapitation and the uteri removed, stripped of adhering fat and mesentery and weighed on a Cahn Electrobalance. Uterine dry weights were measured with a Mettler Analytical Balance after drying (90 C) to constant weight. Uterine DNA synthesis was measured as described by Kaye et al. (13). Uteri were incubated in Eagle's HeLa Medium (Difco) for 1 h at 37 C with 0.25 /iCi [3H]thymidine (Schwarz/Mann) per ml and a total thymidine concentration of 4 x 10~6M. Incubations were performed under 95% O2/5% CO2 with gentle shaking. Following the incubation the uteri were homogenized, and nucleic acids and proteins were precipitated by perchloric acid (PCA; 0.25N) at 0 C. After washing, the pellets were hydrolyzed at 90 C for 30 min in the presence of 0.4N PCA. Aliquots of the final supernatants were then counted to determine [3H]thymidine incorporation. The conversion of 2-deoxyglucose to 2-deoxyglucose-6-phosphate was measured as described by Gorski and Raker (16). Uteri were incubated in Eagle's HeLa Medium containing 0.5 /iCi/ml of [l- 14 C]2-deoxyglucose (New England Nuclear) for 30 min at 37 C under an atmosphere of 95% 0^5% CO2. Following homogenization and removal of PCA-insoluble material, the samples were adjusted to alkaline

Endo • 1977 Vol 101 • No 2

pH (approximately 8.0) and insoluble potassium perchlorate was removed by centrifugation. The 14C-labelled 2-deoxyglucose-6-phosphate formed was then absorbed with BIO-RAD Ag2x8 resin in a batch procedure, the resin was washed 3 times with 4.0 ml of distilled water and then extracted with HC1 (0.2N) to remove the 2-deoxyglucose-6-phosphate for counting. Protein content was measured by a modification (17) of the method of Lowry et al., and RNA content was measured by the orcinol reaction (18). For measurement of the affinity of cytoplasmic estrogen receptors for estradiol, uteri from OVX or OVX-HX rats were homogenized in 0.05M Tris, pH 7.4, containing 1.5 mM EDTA, and cytosol was prepared by centrifugation at 100,000 X g for 1 h. Aliquots of cytosol were then incubated overnight at 0-4 C with concentrations of [3H]estradiol (New England Nuclear) between 1 x 10"10 and 5 x 10"8M. Parallel incubations containing the same amounts of labelled hormone plus 100-fold excesses of unlabelled hormone were used to assess non-specific binding at each concentration of labelled hormone. The amounts of free and bound hormone were then determined using the hydroxylapatite procedure described by Williams and Gorski (19). The data from both groups were analyzed by the method of Scatchard (20), and in both cases single lines with identical slopes were obtained. The sedimentation coefficients of nuclear receptors formed by the in vitro incubation of uteri with [3H]estradiol were measured exactly as previously described (21), including the use of parallel incubations with excess cold hormone to insure that the observed peaks represented specific hormone binding. The total content of nuclear "translocatable" estrogen receptors was measured as follows. Uteri were incubated under 95% 0^5% CO2 in Eagle's HeLa Medium containing either 1 x 10"8M [3H]estradiol or 1 x 10"8M [3H]estradiol plus a 100-fold excess of unlabelled estradiol to assess non-specific binding. After a 1 h incubation at 37 C, the uteri were homogenized at 0 C in 0.05 M Tris, pH 7.4, containing 1.5 mM EDTA, and the homogenates centrifuged at 800 x g for 10 min to obtain the nuclear-myofibrillar pellet. The pellet was then washed and extracted with 95% EtOH to determine the amount of specifically bound hormone in the nuclear fraction (22).


ESTROGEN ACTION AFTER HYPOPHYSECTOMY

FIG. 1. Effect of hypophysectomy on uterine wet weight 24 h after estradiol (E2) treatment. OVX or OVX-HX animals were treated with the indicated doses of E2 24 h prior to sacrifice. The values represent the mean uterine weights (n = 5-9 for each point) with the indicated

405

z g UJ

SEM.

0 0.01 0.2 4.0 20.0 DOSE E2 (ug/100g body weight)

Results

levels, hypophysectomy produced a decrease in the magnitude of the maximum uterine response, but did not appear to shift the dose response curve for E2. In contrast to its effect on OVX-HX animals, E2 treatment (4 /Ltg/lOOg body weight) of OVXSham HX animals produced an increase of 188 ± 13% relative to saline-treated control animals in the same group. This increase was not significantly different from the OVX group. Similarly, Fig. 2 illustrates the increases in total uterine protein content observed 24 h after hormone treatment. It is clearly

Initially we sought to determine the effect of hypophysectomy on the uterine responses to estradiol (E2) 24 h after administration. Figure 1 illustrates the increases in uterine wet weight observed 24 h after administration of increasing doses of E2 to OVX animals and to OVX-HX animals. Maximum doses of E 2 produced an approximate doubling in uterine weight in the OVX group, but only small increases (125-130% of controls) in the OVX-HX animals. Since responses of both groups reached plateau 6

FiG. 2. Effect of hypophysectomy on uterine protein content 24 h after estradiol (E2) treatment. OVX or OVX-HX animals were treated with the indicated doses of E2 24 h prior to sacrifice. The values represent die means of total uterine protein content (n = 5-9 for each point) with the indicated SEM.

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406

Endo • 1977 Vol 101 • No 2

KIRKLAND ET AL.

TABLE 1. Effect of hypophysectomy on uterine responses to estradiol (E2) 24 h after treatment Treatment Saline

Parameter

Response as % of saline control

E2

Uterine RNA content (/ug/uterus)

ovx OVX-HX OVX-Sham HX Uterine dry weight (mg/uterus) OVX OVX-HX Uterine DNA synthesis (cpm [3H]thymidine incorporated/uterus x 10~3) OVX OVX-HX

158 68 189

± 9 ± 10 ± 18

3.4 ± 0.3 2.1 ± 0.2

(7) (7) (7)

(6)

(6)

6.57 ± 0.55 (7) 3.60 ± 0.80(13)

413 107 456

dt 30 it 11 dt 90

9.5:t 0.9 3.0: t 0.2

(7) (7) (7)

260 156 243

(6) (6)

278 dt 138 dt

86.2 ± 21.2 (7) 14.2 ± 1.68 (10)

dt 13 dt 15 dt 34

27 11

1,311 ± 323 393 ± 47

The indicated groups of animals were treated with E2 (4/xg/100 g body weight) or the vehicle alone (saline) 24 h prior to sacrifice. All values represent the mean ± SEM with the number of animals used for each determination in parentheses. E2 treatment produced significant increases (P < 0.05) in all parameters measured in all groups of animals, but increases produced by E2 treatment (response as % of saline control) in OVX animals are significantly different from those produced in OVX-HX animals for all parameters: RNA content (P < 0.002); dry weight (P < 0.001); DNA synthesis (P < 0.001).

seen that E2 produced a large increase (an approximate doubling) in the OVX animals, but no significant increase in the OVX-HX animals. In OVX-Sham HX animals, E2 treatment (4 /xg/100 g body weight) produced an increase in uterine protein content of 231 ± 20% relative to saline-treated controls, and this increase was essentially the same as the increase seen in the OVX group at the same dose level (204 ± 18%). It should be mentioned that results of this nature are somewhat variable from one experiment to the next. In other experiments, for example, E2 treatment has produced significant increases in uterine protein content in OVX-HX animals, but the relative increases are always less than half those seen in OVX animals and are routinely only 20 to 30% of those seen in OVX animals. In addition to measuring increases in uterine wet weight and protein content in OVX and OVX-HX animals we have also measured estrogen-induced increases in uterine dry weight, RNA content and the incorporation of tritiated thymidine into the DNA of surviving uteri in an in vitro test system (Table 1). E2 treatment did produce significant increases in all of these parameters in the OVX-HX animals, but it is clear that in all cases the OVX-HX animals

showed greatly diminished responses relative to the OVX animals. Since all of the measurements to this point were made 24 h after E2 treatment it was of interest next to observe the effect of hypophysectomy on uterine responses occurring at shorter times after hormone administration. The data in Fig. 3 illustrate the increases in uterine wet weight which occurred 4 h after hormone treatment. It is clear that hypophysectomy does not diminish this early uterine response to E2, since the response of the OVX-HX animals (relative to saline-treated controls) is actually slightly increased relative to the OVX group in this particular experiment. In addition to measuring the increase in uterine wet weight 4 h after E2 treatment, we have also measured the increase in the production of 2-deoxyglucose-6-phosphate from 2-deoxyglucose at this early time after hormone administration (Fig. 4). The data in Fig. 4 illustrate that both OVX and OVX-HX animals showed essentially identical increases in the formation of 2deoxyglucose-6-phosphate at this early time after treatment. This is a particularly interesting parameter, since Gorski and Raker (8) showed that increases in this parameter occur in a bi-phasic manner after


407

ESTROGEN ACTION AFTER HYPOPHYSECTOMY

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E2 administration. These investigators reported that 2-deoxyglucose-6-phosphate formation is rapidly elevated (3-8 h) after E 2 treatment, decreases and then increases to a second maximum (24 h). It was therefore of interest to examine this parameter 24 h after hormone administration to both OVX and OVX-HX animals. The results of these studies (Fig. 5) indicate that this "late" response is not significantly affected by hypophysectomy. Although the uterine response is slightly diminished in the OVX-HX animals (233 ± 15% relative to saline treated controls) compared

FIG. 4. Effect of hypophysectomy on uterine 2deoxyglucose-6-phosphate (2-DGP) synthesis 4 h after estradiol (E2) treatment. OVX or OVX-HX animals were treated with E2 (4 fig/100 g body weight) or the vehicle alone (C) 4 h prior to sacrifice. The indicated values represent the mean levels of 2-DGP synthesis (see Materials and Methods) with the indicated SEM (n = 8 for all groups).

30

to the OVX group (281 ± 45%) the difference between these two groups is not significant and is clearly not as great as that observed when other parameters were measured (see UJ Figs. 1 and 2 and Table 1). In an initial attempt to determine the underlying basis for the diminished longterm uterine responses to estrogens in OVXHX animals relative to OVX animals we examined the structure, content and affinity of uterine estrogen receptors in the two groups. Based on these three criteria we C E2 C E2 could not discern any differences in the naFIG. 3. Effect of hypophysectomy on uterine wet ture or content of estrogen receptors in the weight 4 h after estradiol (E2) treatment. OVX or two groups. Thus, receptors extracted from OVX-HX animals were treated with E2 (4 /xg/100 g uterine nuclei of both OVX and OVX-HX body weight) or the vehicle alone (C) 4 h prior to animals sedimented at 5.1 S in sucrose gradisacrifice. The indicated values represent mean uterine weights with the indicated SEM. (n = 8 for ents containing 0.4M KC1, cytosol receptors from both groups of animals had the same each determination). UJ


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KIRKLAND ET AL.

Endo • 1977 Vol 101 • No 2

tain uterine responses to E2. Specifically, hypophysectomy diminishes long-term OVX uterine growth responses such as increased weight, DNA synthesis, RNA and protein content (Figs. 1 and 2 and Table 1). On the 55 other hand, early uterine responses to E2 UJ are not diminished by hypophysectomy (Figs. 3 and 4) and at least one late response, phosphorylation of 2-deoxyglucose, * 10 is not diminished (Fig. 5). At present, we do not know the underlying basis for this OVX-HX selective decrease in certain responses, but our observations appear to rule out several possibilities. One possibility which we have investigated is that hypophysectomy might alter ° e the content and/or properties of uterine estrogen receptors and this might account for the diminished responses. This possiO bility seems unlikely for several reasons. >First, in vitro studies indicated that the X O content, sedimentation coefficient and afUJ finity of receptors for E2 are similar in OVX Q and OVX-HX animals. Furthermore, several uterine responses to E2, e.g., early increases in wet weight and phosphorylation of 2deoxyglucose, occur normally and these reC E2 C E2 sponses are presumably mediated by the FIG. 5. Effect of hypophysectomy on uterine 2-deoxygluestrogen receptor system. cose-6-phosphate (2-DGP) synthesis 24 h after estradiol The most likely explanation for these ob(E2) treatment. OVX or OVX-HX animals were treated servations seems to be that a pituitary facwith E2 (4 /j,g/100 g body weight) or the vehicle alone tors) is required for the complete uterine (C) 24 hours prior to sacrifice. The indicated values response to E to occur normally. It is not 2 represent the mean levels of 2-DGP synthesis (see Materials and Methods) with the indicated SEM. (n possible to determine at present if such a = 7 for all groups). factor acts directly on the uterus or indirectly via another organ. Since all the animals used affinity for E2 (Kd = 1.4 X 10- 10 M), and when in this study were ovariectomized, however, corrected for differences in weight uteri we can conclude that if this is an indirect from both groups had the same content of effect it is not mediated by ovarian steroids. "nuclear translocatable" receptors (0.51 Previous studies of the effect of hypo± 0.05 pmoles per 25 mg wet weight in physectomy on estrogen-induced uterine the OVX group and 0.48 ± 0.01 pmoles per growth have yielded conflicting results. 25 mg wet weight in the OVX-HX group). Muhlbock and van Maurik (24) reported that These values are all in good agreement with increases in uterine weight resulting from numerous measurements reported in the estrogen treatment were greater in HX than literature (6,22,23). in OVX infantile mice, while Hill and Parkes (25) observed no differences in the Discussion responses between OVX and OVX-HX The results of this study illustrate that ferrets. Huggins et al. (26) further reported hypophysectomy selectively affects cer- that low doses of estrone (0.1-0.5 /i,g) in-

15

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ESTROGEN ACTION AFTER HYPOPHYSECTOMY creased uterine weight to a greater degree in HX rats than in OVX rats, but no differences were noted at higher doses (0.5-1.0 /u.g). It has also been reported that E 2 treatment produces similar uterine responses in OVX and OVX-HX-adrenalectomized rats (27). In addition several groups have reported that the administration of exogenous growth hormone increases uterine weight in hypophysectomized animals (26,28). In contrast to our results, most previous studies have thus found that hypophysectomy enhances or does not affect the uterine response to estrogen. The precise reason for this discrepancy is unclear, but several major differences in experimental procedures may be responsible. For example, our studies were performed by hypophysectomizing immature rather than mature rats (27), and it is possible that an intact pituitary is required for the complete uterine response only during a specific developmental period. Liu (29), for example, reported that the response of the rat uterus to estrogens varied between 20 and 50 days of age. Also, we have studied the uterine response following the administration of a single dose of E 2 while all the studies cited above used multiple estrogen injections (24-27). Many previous studies have also used estrogens other than E 2 to evaluate uterine responses. Huggins et al. (26), and Muhlbock and van Maurik (24) used estrone and Hill and Parkes (25) used "trihydroxy oestrin." Finally, it is obvious from our findings that the specific response(s) of the uterus to estrogens as well as the time at which specific responses are measured are both important for assessing the overall effect of hypophysectomy. In addition to our studies, several other lines of reasoning suggest that a factor(s) other than estrogens may be required to produce what are commonly thought to be estrogen-mediated growth processes. For example, it has not been possible to demonstrate estrogen dependent growth of uterine tissue in vitro despite attempts by many investigators, but it is possible to produce

409

other in vitro responses of uterine tissue to estrogens (30,31). In the latter cases, the responses which are produced in vitro occur quite rapidly in vivo and thus are "early" uterine responses. Similarly, certain established cell lines exhibit an absolute dependence on estrogens for in vivo tumor formation in suitable hosts, but are not affected by estrogens when grown in tissue culture (32). Both these observations thus seem to indicate that a factor(s) other than estrogen plays an important role in estrogen-stimulated growth responses. Based upon our results with hypophysectomized animals and the extensive studies of numerous other investigators we have thus adopted the following model as a working hypothesis to explain the overall uterine response to E2. Estradiol enters uterine cells, combines with specific cytoplasmic receptors and migrates to the uterine nuclei (15,23). Based upon the work of others, this initial sequence of events alone appears to be sufficient to produce "early" uterine responses to E2 occurring within 3-4 h, e.g., increases in wet weight (5-7), the synthesis of the so-called IP or induced uterine protein (30), increases in glucose metabolism (7-9), etc. An extended retention (approximately 6 h) of receptorestrogen complexes in uterine nuclei is then necessary for all long term uterine responses (produced 24 h after treatment) to occur (5), and sufficient for some long term uterine responses to occur, e.g., phosphorylation of 2-deoxyglucose. In addition to extended nuclear retention of hormonereceptor complexes another factor(s), which has not been previously recognized, is required for most long term uterine responses to occur normally. The nature, site of production and mechanism of action of this putative factor are unknown at this time, and studies designed to answer these questions are currently in progress. References 1. Szego, C. M., and S. Roberts, Recent Prog Horm Res 8: 419, 1953.


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2. Mueller, G., A. Herranen, and K. Jervell, Recent Prog Horm Res 41: 95, 1958. 3. Hisaw, F. L., Jr., Endocrinology 64: 276, 1959. 4. Hechter, O., and. I. Halkerston, In Pincus, G., K Thimann, and E. Astwood (eds.), The Hormones, vol. 5, Academic Press, New York, 1964, p. 786. 5. Clark, J. H., E. J. Peck, Jr., and J. N. Anderson, J Toxicol Environ Health 1: 561, 1976. 6. Anderson, J. N., J. H. Clark, and E. J. Peck, Jr., Biochem Biophys Res Commun 48: 1460, 1972. 7. Anderson, J. N., E. J. Peck, Jr., and J. H. Clark, Endocrinology 92: 1488, 1973. 8. Gorski, J., and B. Raker, Gynecol Oncol 2: 249, 1974. 9. Lan, N. C , and B. S. Katzenellenbogen, Endocrinology 98: 220, 1976. 10. Hardin, J. W., J. H. Clark, S. R. Glasser, and E. J. Peck, Jr., Biochemistry 15: 1370, 1976. 11. Webster, R. A., and T. H. Hamilton, Biochem Biophys Res Commun 69: 737, 1976. 12. Glasser, S. R., F. Chytil, and T. C. Spelsberg, Biochem J 130: 949, 1972. 13. Kaye, A. M., D. Sheratzky, and H. R. Lindner, Biochim Biophys Ada 261: 475, 1972. 14. Mueller, G. C , In Pincus, G. (ed.), Biological Activities of Steroids in Relation to Cancer, Academic Press, New York, 1960, p. 129. 15. Gorski, J., and F. Gannon, Ann Rev Physiol 38: 425, 1976. 16. Gorski, J., and B. Raker, Endocrinology 93: 1212, 1973.

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17. Lowry, O. H., N. J. Rosebrough, A. L. Farr, and R. J. RandallJ Biol Chem 193: 265, 1951. 18. Shatkin, A. J., In Habel, K., and N. P. Saltzman (eds.), Fundamental Techniques in Virology, Academic Press, New York, 1969, p. 231. 19. Williams, D. W., and J. Gorski, Proc Natl Acad Sci USA 69: 3464, 1972. 20. Scatchard, G., Ann NY Acad Sci 51: 66, 1949. 21. Stancel, G. M., and J. Gorski, Methods Enzymol 36: 251, 1974. 22. Juliano, J. V., and G. M. Stancel, Biochemistry 15: 916, 1976. 23. Jensen, E. V., and E. R. DeSombre, Ann Rev Biochem 41: 203, 1972. 24. Muhlback, O., and G. von Maurick, Ada Physiol Pharmacol Neerl 2: 80, 1951. 25. Hill, M., and A. S. Parkes, Proc R Soc Lond [Biol] 113: 541, 1941. 26. Huggins, C , E. V. Jensen, and A. S. Cleveland, J Exp Med 100: 225, 1954. 27. Velardo, J. T., Ann NY Acad Sci 75: 441, 1959. 28. Grattarola, R., and C. H. Li,Endocrinology 65: 802, 1959. 29. Liu, F. T. Y., Am J Physiol 198: 1255, 1960. 30. Katzenellenbogen, B. S., and J. Gorski, / Biol Chem 247: 1299, 1972. 31. Pietras, R. J., and C. M. Szego, Endocrinology 96: 947, 1975. 32. Sirbasku, D. A., and W. L. Kirkland, Endocrinology 98: 1260, 1976.


The effect of hypophysectomy on the quail's oviduct response to low and high doses of estradiol benzoate.

Effect of estradiol on the early incorporation of (3H) thymidine into uterine DNA on immature mouse.

Changes in the apical microfilaments of rat uterine epithelial cells in response to estradiol and progesterone.

The effect of ether on formation and dissociation of rat uterine estradiol-receptor complex.

Effect of phenols on the oxidation of estradiol by uterine peroxidase.

Hypophysectomy and saralasin on mesenteric vasoconstrictor response to vasopressin.

Perinatal exposure to androgen excess and the effects on the rat uterine estradiol responsiveness.

Effect of pregnancy on the uterine vasoconstrictor response to exercise in rats.

Effect of oxytocin and estradiol on uterine prostaglandin release in nonpregnant and early-pregnant ewes.

Two binding sites for estradiol in rat uterine nuclei: relationship to uterotropic response.

The effect of hypophysectomy on the function of the insulin-sensitive central nervous system glucoregulator receptor.

Effect of hypophysectomy on the chemical composition and intermediary metabolism of the Japanese eel, Anguilla japonica.

The effect of ethinyl estradiol on endometrial thickness and uterine volume during ovulation induction by clomiphene citrate.

Effect of fetal hypophysectomy on the initiation of parturition in the goat.

Regulation of uterine responsiveness to injected estradiol in nutritionally stressed ovariectomized rats by adrenal-dervied estradiol.

Effect of actinomycin D and estradiol on the response to LH-releasing hormone in neonatally androgenized femal rats.

Effect of hypophysectomy and insulin on lipogenesis in cockerels.

Effect of hypophysectomy on rat preadipocyte replication and differentiation.

Effect of stilbestrol on the uterine phosphatases of the rabbit.

The effects of hypophysectomy on liver glycogenolytic enzymes and starvation response in goldfish (Carassius auratus L.).

Effects of hypophysectomy and prolactin replacement therapy on prostatic response to androgen in orchiectomized rats.

Filtration of calf uterine cytosol on ultrogel ACA 34 prevents aggregation of the estradiol receptor.

Structural response of the hamster Sertoli cell to hypophysectomy: a correlative morphometric and endocrine study.

Response of adenocarcinoma of the uterine cervix to chemoradiotherapy.