Life Sciences, Vol . 23, pp . Printed in the U .S .A .
Pergamon Press
1813-1818
THYROTROPIN RELEASING HORMONE (TRH) IS NOT THE PHYSIOLOGICAL PROLACTIN RELEASING FACTOR (PRF) IN THE MALE RAT S . H . Shin Department of Physiology, Abramsky Hall, Queen's University, Kingston, Ontario, Canada K7L 3N6 (Received in final form September 5,
1978)
Summa -rar Thyrotropin releasing hormone (TRH) is known to stimulate prolactin secretion but it is not known whether TRH is the physiological prolactin releasing factor (PRF) or whether the TRH effect on prolactin secretion is a pharmacological action . Normal male rats were implanted with permanent right atrial cannulae and sequential blood samples were taken every min through the cannula . Ether stress elevated plasma prolactin to more than 3 times the normal concentration, while plasma TSH was not changed . However, TRH raised plasma TSH to more than 5 times the normal concentration, while the elevation of plasma prolactin concentration was marginal . The dissociation between the elevation of plasma TSH and prolactin concentrations with ether stress and TRH injection indicates that TRH is not the physiological PRF . It is well established that hypothalamic prolactin inhibiting factor (PIF) plays an important role in the control of the basal secretion of adenohypophysial prolactin (1, 2, 3) . There is also evidence that certain fractions derived from hypothalamic extract are capable of stimulating prolactin secretion . However, the only chemically characterized component in hypothalamic extract which has a stimulating effect on prolactin secretion is TRH (4) . Many investigators believe that TRH is a good candidate for the physiological prolactin releasing factor (PRF) (5, 6) . As yet it is not established whether TRH is the physiological PRF or whether the TRH effect on prolactin secretion is a mere pharmacological action . In addition to TRH, there are several putative PRFs for which the chemical structures are not established (7, 8, 9, 10, 11) . We have undertaken to determine whether TRH is the physiological PRF by examining the relationships between plasma TSH and prolactin concentrations under several different conditions . Materials and Methods Two weeks before the experiment, young male Sprague-Dawley rats (Charles River, CD, Canadian Breeding Farms and Laboratories) were housed in group cages in a controlled environment with illumination for 14 hr a day (0600-2000 hr) and a temperature of 25° t 1°C . Purina lab Chow and tap water were supplied ad libitum. Each rat was weighed (350 t 30 g) and injected with 0300-9653/78/1030-181302 .00/0 Copyright (c) 1978 Pergamon Press
1814
TRH Not the Physiological PRF
Vol . 23, Nos . 17 $ 18, 1978
pentobarbital, U.S .P . (Hater-Lockhart Lab ., Calgary, Alberta) (45 mg/kg), intraperitoneally . Silastic tubing (0 .025" ID, 0 .047" OD, Dow Corning Corporation, Midland, Michigan) was inserted into the right jugular vein and was gently introduced into the right atrium . The other end of the Silastic tubing was advanced to the back of the neck through a subcutaneous tunnel . A section of the tubing was strengthened by the external application of polymerizing elastomer (Dow Corning Corporation) to prevent the tubing from collapsing when it was tied to the neck muscles with thread . The Silastic tubing was filled with heparinized (50 U/ml ; from porcine intestinal mucosa, Grade II, Sigma Chemical Co ., St . Louis, Mo .) 10$ polyvinyl pyrrolidone K-90 (PVP, Nutritional Biochemicals, Cleveland, Ohio) solution and backflow was prevented by inserting a polyethylene plug . The rats with indwelling cannulae were housed in single cages for 1 or more days . One day before the experiment, animals were placed in sampling cages (22 x 11 x 11 cm3) which were equipped with a one-way observation glass . The PVP solution was removed 1 hr before experimentation and 1 ml of heparinized saline (500 U/ml) was gently injected through the cannula . The end of the tubing was fitted with polyethylene tubing (PE 60, Intramedia, 0 .030" ID, 0 .048" OD, Clay Adams, Parsippany, N .J .) for sampling blood . The total dead space of the sampling tube was 200 ul . Approximately 70 ul of blood was withdrawn every minute into a heparinized microhematocrit capillary tube (Fisher Scientific Co .) and the tube was sealed with Critoaeal (Sherwood Medical Industries, St . Louis, Mo .) . The blood sample was centrifuged in a microhematocrit centrifuge (IEC Model MB) for 10 min at 11,500 rpm. The hematocrit tube was cut and plasma samples were harvested. The odd numbered blood samples were assayed for prolactin and the even numbered for TSH . Triplicate samples of 10 yl plasma were assayed using radioimmunoassay kits for rat prolactin or for rat TSH which were kindly supplied by Dr . A . F. Parlow through the NIAMDD Rat Pituitary Hormone Distribution Program . The quantities of prolactin and TSH were expressed in terms of NIAMDD prolactin RP-1, and of NIAMDD TSH RP-1 . Results When 7 individual male rats were exposed to ether by placing them in an ether-saturated glass jar for 3-4 min, the plasma prolactin level was elevated to more than 3 times the normal concentration, while an elevation of plasma TSH was not seen (Fig . 1 represents typical responses in 2 rats) . On the other hand, a bolus injection of TRH (600 yg/kg) through the indwelling cannula elevated the circulating TSH concentration to more than 5 times the normal value in 7 individual rats . However, stimulation of prolactin secretion by fiRH (600 ug/kg) was inconsistent, the increment of the plasma prolactin level being less than 30$ over the normal concentration (Fig . 2 represents typical responses in 2 rats) . Discussion It is well known that ether stress stimulates prolactin secretion (12, 13, 14, 15, 16) . It was demonstrated that the prolactin secretion induced by ether stress is due to the stimulation of PRF secretion rather than to the inhibition of PIF secretion (17, 27) . However, the chemical nature of the physiological PRF is not known . One of the leading candidates for the physiological PRF is TRH, since TRH will stimulate prolactin secretion (4) .
Vol . 23, Nos . 17 $ 18, 1978
TRH Not the Physiological PRF
ETHER 79" 28 78519
E 2000 c
a
1000
a
80 60r
50
E 40 Z
Q a a a
30
/r I
20
10
/ ~ .~~1~ ~
~50~ ~ o ô
d
19
T
39
59
SAMPLE NUMBER
79
FIG . 1 The effect of ether on prolactin and TSH secretion in normal male rats . The upper panel represents TSH concentration and the lower panel shows the temporal changes in the circulating prolactin level . Two representative results from 7 individual experiments are shown . Open and closed squares represent 2 different rats . Arrows (?) indicate administration of ether . Since blood samples were withdrawn every min, the sample number in the abscissa is same as time in min .
1815
1816
TRH Not the Physiological PRF
Vol . 23, Nos . 17 $ 18, 1978
TRH(60%ig/kg)
78322 78323
~ 4000 w v~ c
a â 2000
20
40
60
80
30
a a g a
°
° °ô~
d'~ ô~i ï 19
'
i' "~i;1! " '" "
ô~ "
t
59 79 39 SAMPLE NUMBER FIG. 2
The effect of a bolus injection of TRH (600 ug/kg) on prolactin and TSH secretion in normal male rats . The upper panel represents TSH concentration and the lower panel prolactin concentration . Two representative results from 7 individual experiments are shown . Open and closed squares represent 2 different rats . Arrows (?) indicate administration of TRH . Since blood samples were withdrawn every min, the sample number in the abscissa is same as time in min .
Vol . 23, Nos, 17 P, 18, 1978
TRH Not the Physiological PRF
1817
We have now examined the relationship between plasma TSH and prolactin concentration in two different situations in order to clarify whether the stimulatory effect of TRH on prolactin secretion is a physiological or pharma cological action . We took sequential blood samples every min and then assayed for prolactin and TSH in alternate plasma samples to closely examine the temporal responses to the stimulating agents . The conscious, freely moving rat preparation with an indwelling cannula is ideally suited for sequential blood sampling, since such a preparation can circumvent artifacts caused by handling and manual injection (16) . The volume of the blood samples was limited to 70 ul in order to avoid possible stress due to loss of blood . We prefer to perform the radioimmunoassays (RIA) for each blood sample in triplicate and the plasma volume we used for the RIA was 10 yl . The NIAMDD RIA kit for prolactin was sufficiently sensitive to assay basal prolactin levels in 10 ul of plasma . However, since the lower limit of sensitivity of the TSH RIA is about 5 ng and since we assay 10 ul samples, assayed values for plasma TSH of less than 500 ng/ml are not reliable . Thus the basal plasma TSH levels recorded are at the lower limit of sensitivity of the assay . Ether stress, as expected, augmented markedly the secretion of prolactin (Fig . 1) while the simultaneously measured TSH levels remained unchanged . It has been reported (18) that ether stress actually lowers circulating TSH . We would not have been able to detect such a reduction using 10 yl plasma samples . TRH is known to stimulate TSH as well as prolactin secretion in man (19, 20), cow (21, 22) and sheep (23) . In ovariectomized rats, TRH had no effect on plasma prolactin but TRH did induce a significant increase in plasma prolactin in the estrogen primed rat (24) . In the male rat, TRH has been shown to have a small effect on prolactin secretion but these investigators did not measure TSH (25, 26) . These results are consistent with our findings (Fig . 2) . The effect of TRH was to very greatly augment TSH secretion, while prolactin secretion, measured concurrently, was barely altered in the same rats . The secretion of prolactin and TSH are completely dissociated in the two cases we have tested . Ether stress results in a marked increase in prolactin release with no concurrent increase in TSH release, xhile TRH induces a marked increase in TSH release with no concurrent change in prolactin release . Therefore, we conclude that the TRH is not the physiological PRF . Acknowle~ements This work was supported by the Medical Research Council of Canada . The author wishes to thank Dr . A . F . Parlow of the NIAMDD Rat Pituitary Hormone Distribution Program for the prolactin radioimmunoassay kit, and Dr . Kraicer and Dr . A . E . Zimmeruran for help with the preparation of the manuscript, and Miss S . Ball for excellent typing . References 1. 2. 3. 4. 5.
J . W . EVERETT, Endocrinology 54 685-690 (1954) . J . MEITES and C . S . NICOLL, Ann . Rev . Physiol . 28 57-88 (1966) . S . M . MCCANN and J . C . PORTER, Physiol . Rev . 49 240-284 (1969) . A . H . TASJIAN, N . J . BROWSKY and D . K . JENSEN,Biochem . Biophys . Res . Commun . 4 3 516-523 (1971) . A . G . FRANTZ, H othalamic Pe tide Hormones and Pituita Re lation, pp . 279-298, ed . J . C . Porter, Plenum Press, New York 1977 .
1818
6. 7. 8. 9. 10 . 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 . 20 . 21 . 22 . 23 . 24 . 25 . 26 . 27 .
TRH Not the Physiological PRF
Vol . 23, Nos . 17 $ 18,
1978
R . M . MACLEOD, Frontiers in Neuroendocrinolo , Vol . 4, pp . 169-194, eds . L . Martini and W . . Ganong, Raven Press, ew York (1976) . R . DULAR, F . LABELLA, S . VIVIAN and L . EDDIE, Endocrinology 94 563-567 (1974), T . KOKUBU, S . SAWANO, M . SHIRAKI, M . YAMASAKI and Y . ISHIZUKA, Endocrinol . japon . _22 213-217 (1975) . C . VALVERDE-R, V . CHIEFFO and S . REICHLIN, Endocrinology _91 982-993 (1972), M . SZABO and L . A . FROHMAN, Endocrinology 98 1451-1459 (1976) . A . E . BOYD, III, E . SPENCER, I . M . D . JACKSON and S . REICHLIN, Endocrinology _99 861-871 (1976) . I . WAKABAYASHI, A . ARIMURA and A . V . SCHALLY, Proc . Soc . Exp . Biol . Med . 13 7 1189-1193 (1971) . . L KRULICH, E . HEFCO, P . ILLNER and C . B . READ, Neuroendocrinology _16 293-311 (1974) . C . E . SIMONEL, C . L . BROOKS and C . W . WELSCH, Experientia _31 688-789 (1975) . C . TURPEN, D . C . JOHNSON and J . D . DUNN, Neuroendocrinology _20 339-351 (1976), H . J . CHI and S . H . SHIN, Neuroendocrinology _26 193-201 (1978) . S . H . SHIN, 60th Ann . Mtg . Endocrine Soc ., Abst . #756 (1978) . C . FORTIER, A . DELGADO, P . DUCOMMUN, S . DUCOMMUN, A . DUPONT, M . JOHIN, J . KRAICER, B . MACINTOSH-HARDT, H . MARCEAU, P . MIALHE, C . MIALHE-VOLOSS, C . RERUP and P . VAN RÉES, Canad . Med . Assoc . J . 10 3 864-874 (1970) . C . Y . BOWERS, H . G . FRIESEN, P . HWANG, H . J . GpYDA and K . FOLKERS, Biochem . Biophys . Res . Commun . _45 1033-1041 (1971) . D . S . COOPER and L, S . JACOBS, J . Clin . Endocrinol . Metab . _44 404-407 (1977) . E . M . CONVEY, H . A, TUCKER, V . G . SMITH and J . ZOLMAN, Endocrinology _92 471-476 (1973) . P . A . KELLY, K . N . BEDIRIAN, R . D . BAKER and H . G . FRIESEN, Endocrinology 92 1289-1293 (1973) . L . R . FELL, J . K . FINDLAY, I . A . GUMMING and J . R . GODING, Endocrinology 93 487-491 (1973) . R . W . STEVENS and D . M . LAWSON, Life Sci . 20 261-266 (1977) . K . H . LU, C . J . SHAAR, K . H . KORTRIGHT andJ . MEITES, Endocrinology _91 1540-1545 (1972) . C . RIMER and W . VALE, Endocrinology 95 978-983 (1974) . C . VALVERDE-R, V . CHIEFFO and S . REICHLIN, Life Sci . 12 327-335 (1973) .
Pergamon Press
1813-1818
THYROTROPIN RELEASING HORMONE (TRH) IS NOT THE PHYSIOLOGICAL PROLACTIN RELEASING FACTOR (PRF) IN THE MALE RAT S . H . Shin Department of Physiology, Abramsky Hall, Queen's University, Kingston, Ontario, Canada K7L 3N6 (Received in final form September 5,
1978)
Summa -rar Thyrotropin releasing hormone (TRH) is known to stimulate prolactin secretion but it is not known whether TRH is the physiological prolactin releasing factor (PRF) or whether the TRH effect on prolactin secretion is a pharmacological action . Normal male rats were implanted with permanent right atrial cannulae and sequential blood samples were taken every min through the cannula . Ether stress elevated plasma prolactin to more than 3 times the normal concentration, while plasma TSH was not changed . However, TRH raised plasma TSH to more than 5 times the normal concentration, while the elevation of plasma prolactin concentration was marginal . The dissociation between the elevation of plasma TSH and prolactin concentrations with ether stress and TRH injection indicates that TRH is not the physiological PRF . It is well established that hypothalamic prolactin inhibiting factor (PIF) plays an important role in the control of the basal secretion of adenohypophysial prolactin (1, 2, 3) . There is also evidence that certain fractions derived from hypothalamic extract are capable of stimulating prolactin secretion . However, the only chemically characterized component in hypothalamic extract which has a stimulating effect on prolactin secretion is TRH (4) . Many investigators believe that TRH is a good candidate for the physiological prolactin releasing factor (PRF) (5, 6) . As yet it is not established whether TRH is the physiological PRF or whether the TRH effect on prolactin secretion is a mere pharmacological action . In addition to TRH, there are several putative PRFs for which the chemical structures are not established (7, 8, 9, 10, 11) . We have undertaken to determine whether TRH is the physiological PRF by examining the relationships between plasma TSH and prolactin concentrations under several different conditions . Materials and Methods Two weeks before the experiment, young male Sprague-Dawley rats (Charles River, CD, Canadian Breeding Farms and Laboratories) were housed in group cages in a controlled environment with illumination for 14 hr a day (0600-2000 hr) and a temperature of 25° t 1°C . Purina lab Chow and tap water were supplied ad libitum. Each rat was weighed (350 t 30 g) and injected with 0300-9653/78/1030-181302 .00/0 Copyright (c) 1978 Pergamon Press
1814
TRH Not the Physiological PRF
Vol . 23, Nos . 17 $ 18, 1978
pentobarbital, U.S .P . (Hater-Lockhart Lab ., Calgary, Alberta) (45 mg/kg), intraperitoneally . Silastic tubing (0 .025" ID, 0 .047" OD, Dow Corning Corporation, Midland, Michigan) was inserted into the right jugular vein and was gently introduced into the right atrium . The other end of the Silastic tubing was advanced to the back of the neck through a subcutaneous tunnel . A section of the tubing was strengthened by the external application of polymerizing elastomer (Dow Corning Corporation) to prevent the tubing from collapsing when it was tied to the neck muscles with thread . The Silastic tubing was filled with heparinized (50 U/ml ; from porcine intestinal mucosa, Grade II, Sigma Chemical Co ., St . Louis, Mo .) 10$ polyvinyl pyrrolidone K-90 (PVP, Nutritional Biochemicals, Cleveland, Ohio) solution and backflow was prevented by inserting a polyethylene plug . The rats with indwelling cannulae were housed in single cages for 1 or more days . One day before the experiment, animals were placed in sampling cages (22 x 11 x 11 cm3) which were equipped with a one-way observation glass . The PVP solution was removed 1 hr before experimentation and 1 ml of heparinized saline (500 U/ml) was gently injected through the cannula . The end of the tubing was fitted with polyethylene tubing (PE 60, Intramedia, 0 .030" ID, 0 .048" OD, Clay Adams, Parsippany, N .J .) for sampling blood . The total dead space of the sampling tube was 200 ul . Approximately 70 ul of blood was withdrawn every minute into a heparinized microhematocrit capillary tube (Fisher Scientific Co .) and the tube was sealed with Critoaeal (Sherwood Medical Industries, St . Louis, Mo .) . The blood sample was centrifuged in a microhematocrit centrifuge (IEC Model MB) for 10 min at 11,500 rpm. The hematocrit tube was cut and plasma samples were harvested. The odd numbered blood samples were assayed for prolactin and the even numbered for TSH . Triplicate samples of 10 yl plasma were assayed using radioimmunoassay kits for rat prolactin or for rat TSH which were kindly supplied by Dr . A . F. Parlow through the NIAMDD Rat Pituitary Hormone Distribution Program . The quantities of prolactin and TSH were expressed in terms of NIAMDD prolactin RP-1, and of NIAMDD TSH RP-1 . Results When 7 individual male rats were exposed to ether by placing them in an ether-saturated glass jar for 3-4 min, the plasma prolactin level was elevated to more than 3 times the normal concentration, while an elevation of plasma TSH was not seen (Fig . 1 represents typical responses in 2 rats) . On the other hand, a bolus injection of TRH (600 yg/kg) through the indwelling cannula elevated the circulating TSH concentration to more than 5 times the normal value in 7 individual rats . However, stimulation of prolactin secretion by fiRH (600 ug/kg) was inconsistent, the increment of the plasma prolactin level being less than 30$ over the normal concentration (Fig . 2 represents typical responses in 2 rats) . Discussion It is well known that ether stress stimulates prolactin secretion (12, 13, 14, 15, 16) . It was demonstrated that the prolactin secretion induced by ether stress is due to the stimulation of PRF secretion rather than to the inhibition of PIF secretion (17, 27) . However, the chemical nature of the physiological PRF is not known . One of the leading candidates for the physiological PRF is TRH, since TRH will stimulate prolactin secretion (4) .
Vol . 23, Nos . 17 $ 18, 1978
TRH Not the Physiological PRF
ETHER 79" 28 78519
E 2000 c
a
1000
a
80 60r
50
E 40 Z
Q a a a
30
/r I
20
10
/ ~ .~~1~ ~
~50~ ~ o ô
d
19
T
39
59
SAMPLE NUMBER
79
FIG . 1 The effect of ether on prolactin and TSH secretion in normal male rats . The upper panel represents TSH concentration and the lower panel shows the temporal changes in the circulating prolactin level . Two representative results from 7 individual experiments are shown . Open and closed squares represent 2 different rats . Arrows (?) indicate administration of ether . Since blood samples were withdrawn every min, the sample number in the abscissa is same as time in min .
1815
1816
TRH Not the Physiological PRF
Vol . 23, Nos . 17 $ 18, 1978
TRH(60%ig/kg)
78322 78323
~ 4000 w v~ c
a â 2000
20
40
60
80
30
a a g a
°
° °ô~
d'~ ô~i ï 19
'
i' "~i;1! " '" "
ô~ "
t
59 79 39 SAMPLE NUMBER FIG. 2
The effect of a bolus injection of TRH (600 ug/kg) on prolactin and TSH secretion in normal male rats . The upper panel represents TSH concentration and the lower panel prolactin concentration . Two representative results from 7 individual experiments are shown . Open and closed squares represent 2 different rats . Arrows (?) indicate administration of TRH . Since blood samples were withdrawn every min, the sample number in the abscissa is same as time in min .
Vol . 23, Nos, 17 P, 18, 1978
TRH Not the Physiological PRF
1817
We have now examined the relationship between plasma TSH and prolactin concentration in two different situations in order to clarify whether the stimulatory effect of TRH on prolactin secretion is a physiological or pharma cological action . We took sequential blood samples every min and then assayed for prolactin and TSH in alternate plasma samples to closely examine the temporal responses to the stimulating agents . The conscious, freely moving rat preparation with an indwelling cannula is ideally suited for sequential blood sampling, since such a preparation can circumvent artifacts caused by handling and manual injection (16) . The volume of the blood samples was limited to 70 ul in order to avoid possible stress due to loss of blood . We prefer to perform the radioimmunoassays (RIA) for each blood sample in triplicate and the plasma volume we used for the RIA was 10 yl . The NIAMDD RIA kit for prolactin was sufficiently sensitive to assay basal prolactin levels in 10 ul of plasma . However, since the lower limit of sensitivity of the TSH RIA is about 5 ng and since we assay 10 ul samples, assayed values for plasma TSH of less than 500 ng/ml are not reliable . Thus the basal plasma TSH levels recorded are at the lower limit of sensitivity of the assay . Ether stress, as expected, augmented markedly the secretion of prolactin (Fig . 1) while the simultaneously measured TSH levels remained unchanged . It has been reported (18) that ether stress actually lowers circulating TSH . We would not have been able to detect such a reduction using 10 yl plasma samples . TRH is known to stimulate TSH as well as prolactin secretion in man (19, 20), cow (21, 22) and sheep (23) . In ovariectomized rats, TRH had no effect on plasma prolactin but TRH did induce a significant increase in plasma prolactin in the estrogen primed rat (24) . In the male rat, TRH has been shown to have a small effect on prolactin secretion but these investigators did not measure TSH (25, 26) . These results are consistent with our findings (Fig . 2) . The effect of TRH was to very greatly augment TSH secretion, while prolactin secretion, measured concurrently, was barely altered in the same rats . The secretion of prolactin and TSH are completely dissociated in the two cases we have tested . Ether stress results in a marked increase in prolactin release with no concurrent increase in TSH release, xhile TRH induces a marked increase in TSH release with no concurrent change in prolactin release . Therefore, we conclude that the TRH is not the physiological PRF . Acknowle~ements This work was supported by the Medical Research Council of Canada . The author wishes to thank Dr . A . F . Parlow of the NIAMDD Rat Pituitary Hormone Distribution Program for the prolactin radioimmunoassay kit, and Dr . Kraicer and Dr . A . E . Zimmeruran for help with the preparation of the manuscript, and Miss S . Ball for excellent typing . References 1. 2. 3. 4. 5.
J . W . EVERETT, Endocrinology 54 685-690 (1954) . J . MEITES and C . S . NICOLL, Ann . Rev . Physiol . 28 57-88 (1966) . S . M . MCCANN and J . C . PORTER, Physiol . Rev . 49 240-284 (1969) . A . H . TASJIAN, N . J . BROWSKY and D . K . JENSEN,Biochem . Biophys . Res . Commun . 4 3 516-523 (1971) . A . G . FRANTZ, H othalamic Pe tide Hormones and Pituita Re lation, pp . 279-298, ed . J . C . Porter, Plenum Press, New York 1977 .
1818
6. 7. 8. 9. 10 . 11 . 12 . 13 . 14 . 15 . 16 . 17 . 18 . 19 . 20 . 21 . 22 . 23 . 24 . 25 . 26 . 27 .
TRH Not the Physiological PRF
Vol . 23, Nos . 17 $ 18,
1978
R . M . MACLEOD, Frontiers in Neuroendocrinolo , Vol . 4, pp . 169-194, eds . L . Martini and W . . Ganong, Raven Press, ew York (1976) . R . DULAR, F . LABELLA, S . VIVIAN and L . EDDIE, Endocrinology 94 563-567 (1974), T . KOKUBU, S . SAWANO, M . SHIRAKI, M . YAMASAKI and Y . ISHIZUKA, Endocrinol . japon . _22 213-217 (1975) . C . VALVERDE-R, V . CHIEFFO and S . REICHLIN, Endocrinology _91 982-993 (1972), M . SZABO and L . A . FROHMAN, Endocrinology 98 1451-1459 (1976) . A . E . BOYD, III, E . SPENCER, I . M . D . JACKSON and S . REICHLIN, Endocrinology _99 861-871 (1976) . I . WAKABAYASHI, A . ARIMURA and A . V . SCHALLY, Proc . Soc . Exp . Biol . Med . 13 7 1189-1193 (1971) . . L KRULICH, E . HEFCO, P . ILLNER and C . B . READ, Neuroendocrinology _16 293-311 (1974) . C . E . SIMONEL, C . L . BROOKS and C . W . WELSCH, Experientia _31 688-789 (1975) . C . TURPEN, D . C . JOHNSON and J . D . DUNN, Neuroendocrinology _20 339-351 (1976), H . J . CHI and S . H . SHIN, Neuroendocrinology _26 193-201 (1978) . S . H . SHIN, 60th Ann . Mtg . Endocrine Soc ., Abst . #756 (1978) . C . FORTIER, A . DELGADO, P . DUCOMMUN, S . DUCOMMUN, A . DUPONT, M . JOHIN, J . KRAICER, B . MACINTOSH-HARDT, H . MARCEAU, P . MIALHE, C . MIALHE-VOLOSS, C . RERUP and P . VAN RÉES, Canad . Med . Assoc . J . 10 3 864-874 (1970) . C . Y . BOWERS, H . G . FRIESEN, P . HWANG, H . J . GpYDA and K . FOLKERS, Biochem . Biophys . Res . Commun . _45 1033-1041 (1971) . D . S . COOPER and L, S . JACOBS, J . Clin . Endocrinol . Metab . _44 404-407 (1977) . E . M . CONVEY, H . A, TUCKER, V . G . SMITH and J . ZOLMAN, Endocrinology _92 471-476 (1973) . P . A . KELLY, K . N . BEDIRIAN, R . D . BAKER and H . G . FRIESEN, Endocrinology 92 1289-1293 (1973) . L . R . FELL, J . K . FINDLAY, I . A . GUMMING and J . R . GODING, Endocrinology 93 487-491 (1973) . R . W . STEVENS and D . M . LAWSON, Life Sci . 20 261-266 (1977) . K . H . LU, C . J . SHAAR, K . H . KORTRIGHT andJ . MEITES, Endocrinology _91 1540-1545 (1972) . C . RIMER and W . VALE, Endocrinology 95 978-983 (1974) . C . VALVERDE-R, V . CHIEFFO and S . REICHLIN, Life Sci . 12 327-335 (1973) .
