RELATIVE CONCENTRATIONS OF EXTROGEN AND PROGESTERONE IN MILK AND BLOOD, AND EXCRETION OF ESTROGEN IN URINE 1 R. E. Erb z, B. P. Chew 2 and H. F. Keller 2
Purdue University, West Lafayette, I N 47907
Concentrations of progesterone, estrone, estradiol-17/3 and estradiol-17a in prepartum mammary secretions and in milk of cows were indicative of concentrations of these steroids in plasma. Rates of excretion of estrogens in urine reflected concentrations of the estrogens in milk and blood plasma. Concentrations of progesterone in mammary secretions first exceeded concentrations in blood plasma about 5 days prior to calving and may be up to fourfold higher in milk (up to 30 ng/ml) than in blood plasma during lactation. However, compared to daily production rates or to transfer of radioactivity from progesterone, only .06 to .25% of progesterone is excreted in milk. Concentrations of estrogens in milk of untreated cows (3 to 25 days of lactation) averaged (pg/ml) 28 + 2, 13 + 1, 160 + 14, and 202 +- 15 for estrone, estradiol-17/~, estradiol-17a, and total estrogen, respectively. In comparison, concentrations in colostrum on day of calving were 65- to 80-fold higher for estradiol-17/3 and estrone, and eightfold higher for estradiol-17a. Compared to concentrations in blood plasma, concentrations of estradiol-17/3 in mammary secretions were higher prepartum and lower during early lactation, estrone was lower both prepartum and postpartum, and estradiol-17a was lower prepartum but several times higher during early lactation. From 3 to 25 days of lactation, biologically inactive estradiol-17a represented at least 70% of the total estrogen in milk as it does at nearly all times in cow urine. Total estrogen excreted in milk of cows was inversely
proportional to its rate of excretion into urine. The proportions of estrogen excreted in milk varied from 2.6% to .03% for lowest to highest rates of urinary excretion of estrogen. These amounts would be about threefold less (.87 to .004%) if based on total estrogen excreted in urine and feces. (Key Words: Progesterone, Estrogen, Milk, Blood, Urine, Cattle.) INTRODUCTION
It is known that many compounds of endogenous or exogenous origin pass from blood into milk of lactating animals. It is assumed that rate of mammary uptake of compounds, especially those considered contaminants, is proportional to their concentrations in blood. Moreover, rate of transfer into milk is dependent on factors other than concentrations in blood, including molecular size, relative solubilities in aqueous and lipid phases of body tissues and fluids, and other chemical characteristics. Our purpose is to review briefly excretion of progesterone and estrogen in milk, and relate concentrations of these steroids in milk postpartum, and in mammary secretions prepartum, to concentrations in blood plasma. Additionally, comparisons will be made for estrogens in milk, blood and urine. Finally, an attempt will be made to evaluate the relative importance of the mammary gland as an excretory route for progesterone and the estrogens.
MAMMARY UPTAKE AND REMOVAL OF STEROIDS
1Journal paper No. 6479, Purdue University AgriSteroid hormones are normally found in cultural Experiment Station. Presented as part of the symposium on Natural Hormones in Edible Animal milk. It is unknown whether or not they should Products held during the A.S.A.S. meeting at Texas be considered contaminants or compounds of A&M University, August 16, 1976. Publication sup- biological significance. The steroids, estrogen, ported in part by DHEW/PHS/FDA/BVM contract No. progesterone and corticoids, along with the 221-76-0129. protein-peptide hormones, insulin, growth hor2Department of Animal Sciences. 617 JOURNAL OF ANIMAL SCIENCE, Vol. 46, No. 3, 1977
Downloaded from https://academic.oup.com/jas/article-abstract/45/3/617/4700693 by guest on 19 November 2018
SUMMARY
618
ERB, CHEW AND KELLER (Turner, 1958 for review) and estradiol-17/3 (Mollett et al., 1976; Willett et al., 1976) are detectable in milk when relatively large doses are administered to cows. PROGESTERONE A N D ESTROGENS--BLOOD PLASMA. M I L K A N D U R I N E
Progesterone. Concentrations of progesterone in cow's milk have been studied extensively in recent years following its identification by Darling et al. (1972). Interest has centered on its potential use as a clinical tool for study of reproduction, including early diagnosis of pregnancy (Gartland et al., 1976; Gunzler et al., 1975; Hoffmann et al., 1975; Pennington et al., 1975; Pennington et al., 1976a,b,c; Schiavo et al., 1975). Concentrations of progesterone in milk appear to parallel concentrations in plasma (Heap et al., 1973; Hoffmann and Hamburger, 1973; Ginther et al., 1974, 1976; Mauer et al., 1974) and are significantly correlated with milk fat during the estrous cycle and during early pregnancy (Ginther et al., 1976; Hoffmann and Hamburger, 1973 ; Nuti et al., 1975 ; Pennington et al., 1975). General indications are that the concentration of progesterone is two- to four-fold greater in milk than in plasma. This may be due to its relatively greater solubility in lipid than in aqueous media as compared to the estrogens and cortisol. There is much potential for in vivo storage of progesterone in lipids of the mammary gland and its secretions. McCracken (1964) has shown that concentrations of progesterone in body fat of cows were about fiveto 10-fold of that in plasma. Heap et al. (1975b) have shown that about 80% of administered 3H_progesterone entering milk was found in fat, 19% in casein and 1% in aqueous fractions of milk. A b o u t the same distribution was observed when 3 H-progesterone was added to cow's milk in vitro. Therefore, progesterone may be transferred to milk by simple diffusion from blood and concentrated by absorption into milk fat. Concentrations of progesterone in mammay secretions first exceeded concentrations in plasma 4 to 5 days before calving (figure 1). The ratio of concentrations of progesterone in mammay secretion and blood plasma averaged 1.4 prior to calving, 2.6 in colostrum (0 to 2 days of lactation), and 1.8 for 3 to 25 days of lactation in cows untreated with hormones (group UT). The ratio in mammary secretions 0
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mone and prolactin, are essential for mammogenesis and onset of lactation (Erb, 1977 for review). However, we know very little about their significance when, after onset of lactation, hormone-containing milk becomes part of the diet for another individual. Therefore, one view could be that hormones excreted in milk have no positive biological function, and that their concentrations in milk represent "imperfect" removal via the venous and lymphatic circulatory systems. The opposite view would be that hormones in milk are biologically important for onset and maintenance of lactation, whether or not they have biological significance when orally ingested. Studies on steroid production rates in vivo and their uptake, metabolism and removal by the mammary gland showed the latter to be a minor route of excretion (Heap and Linzell, 1966; Challis and Linzell, 1973; Heap et aL, 1975a,b; Patterson and Linzell, 1971). Other studies are in general agreement (Lunaas, 1963; Mollett et al., 1976; Monk et al., 1975; Smith et al., 1975; Turner, 1958; Williams, 1962; Willett et al., 1976). Moreover, extent of excretion via milk varies among steroids and mammalian species. In goats, milk contained less than 1% of cortisol removed from blood plasma by the mammary gland (Patterson and Linzell, 1971). Rather, the hormone was returned to the venous circulation. In goats, progesterone taken from blood by the mammary gland was metabolized and the metabolites were removed by the venous route rather than in milk (Heap et al., 1975a). Bovine mammary glands apparently do not synthesize or metabolize progesterone (Heap et al., 1975b). Progesterone excreted via milk represented no more than 3% of the production rate in goats (Heap and Linzell, 1966; Heap et al., 1975a) and cows (Heap et al., 1975b). Mammary uptake of estrone in lactating goats was tess than 3% of the production rate (Challis and Linzell, 1973) but no comparable data on estrogens were found for cows. There is evidence that total estrogen removed daily in milk of cows may be considerably less than 1% of the total metabolized (Monk et al., 1975; Willett et al., 1976) or injected (Mollett et al., 1976). Even though total estrogen excreted in milk is low, concentrations in prepartum mammary secretions and colostrum appear adequate for biological responses when fed to test animals (Turner, 1958 for review). Likewise, it has been demonstrated that synthetic estrogens
ESTROGEN AND PROGESTERONE
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DAYS Figure 1. Concentrations of progesterone in mammary secretions and blood plasma from 17 cows prior to (~ 4.9 -+ .2 and 3.6 +- .2 ng/ml; 110 samples) and after calving (2.6 -+ .3 and 1.0 -+ .04 ng/ml; 82 samples). Day 0 was day of calving. Data from Keller et al. (1977).
to 2 days after calving in cows milked prepartum was about one-half (1.7) that observed for cows not milked prepartum (Keller et al., 1977). Larger ratios in cows not milked preparturn probably reflected mammary accumulation of progesterone prior to its decrease in plasma 1 to 2 days before calving. This hypothesis is supported by the observation that concentrations of progesterone in mammary secretions were significantly (P
Purdue University, West Lafayette, I N 47907
Concentrations of progesterone, estrone, estradiol-17/3 and estradiol-17a in prepartum mammary secretions and in milk of cows were indicative of concentrations of these steroids in plasma. Rates of excretion of estrogens in urine reflected concentrations of the estrogens in milk and blood plasma. Concentrations of progesterone in mammary secretions first exceeded concentrations in blood plasma about 5 days prior to calving and may be up to fourfold higher in milk (up to 30 ng/ml) than in blood plasma during lactation. However, compared to daily production rates or to transfer of radioactivity from progesterone, only .06 to .25% of progesterone is excreted in milk. Concentrations of estrogens in milk of untreated cows (3 to 25 days of lactation) averaged (pg/ml) 28 + 2, 13 + 1, 160 + 14, and 202 +- 15 for estrone, estradiol-17/~, estradiol-17a, and total estrogen, respectively. In comparison, concentrations in colostrum on day of calving were 65- to 80-fold higher for estradiol-17/3 and estrone, and eightfold higher for estradiol-17a. Compared to concentrations in blood plasma, concentrations of estradiol-17/3 in mammary secretions were higher prepartum and lower during early lactation, estrone was lower both prepartum and postpartum, and estradiol-17a was lower prepartum but several times higher during early lactation. From 3 to 25 days of lactation, biologically inactive estradiol-17a represented at least 70% of the total estrogen in milk as it does at nearly all times in cow urine. Total estrogen excreted in milk of cows was inversely
proportional to its rate of excretion into urine. The proportions of estrogen excreted in milk varied from 2.6% to .03% for lowest to highest rates of urinary excretion of estrogen. These amounts would be about threefold less (.87 to .004%) if based on total estrogen excreted in urine and feces. (Key Words: Progesterone, Estrogen, Milk, Blood, Urine, Cattle.) INTRODUCTION
It is known that many compounds of endogenous or exogenous origin pass from blood into milk of lactating animals. It is assumed that rate of mammary uptake of compounds, especially those considered contaminants, is proportional to their concentrations in blood. Moreover, rate of transfer into milk is dependent on factors other than concentrations in blood, including molecular size, relative solubilities in aqueous and lipid phases of body tissues and fluids, and other chemical characteristics. Our purpose is to review briefly excretion of progesterone and estrogen in milk, and relate concentrations of these steroids in milk postpartum, and in mammary secretions prepartum, to concentrations in blood plasma. Additionally, comparisons will be made for estrogens in milk, blood and urine. Finally, an attempt will be made to evaluate the relative importance of the mammary gland as an excretory route for progesterone and the estrogens.
MAMMARY UPTAKE AND REMOVAL OF STEROIDS
1Journal paper No. 6479, Purdue University AgriSteroid hormones are normally found in cultural Experiment Station. Presented as part of the symposium on Natural Hormones in Edible Animal milk. It is unknown whether or not they should Products held during the A.S.A.S. meeting at Texas be considered contaminants or compounds of A&M University, August 16, 1976. Publication sup- biological significance. The steroids, estrogen, ported in part by DHEW/PHS/FDA/BVM contract No. progesterone and corticoids, along with the 221-76-0129. protein-peptide hormones, insulin, growth hor2Department of Animal Sciences. 617 JOURNAL OF ANIMAL SCIENCE, Vol. 46, No. 3, 1977
Downloaded from https://academic.oup.com/jas/article-abstract/45/3/617/4700693 by guest on 19 November 2018
SUMMARY
618
ERB, CHEW AND KELLER (Turner, 1958 for review) and estradiol-17/3 (Mollett et al., 1976; Willett et al., 1976) are detectable in milk when relatively large doses are administered to cows. PROGESTERONE A N D ESTROGENS--BLOOD PLASMA. M I L K A N D U R I N E
Progesterone. Concentrations of progesterone in cow's milk have been studied extensively in recent years following its identification by Darling et al. (1972). Interest has centered on its potential use as a clinical tool for study of reproduction, including early diagnosis of pregnancy (Gartland et al., 1976; Gunzler et al., 1975; Hoffmann et al., 1975; Pennington et al., 1975; Pennington et al., 1976a,b,c; Schiavo et al., 1975). Concentrations of progesterone in milk appear to parallel concentrations in plasma (Heap et al., 1973; Hoffmann and Hamburger, 1973; Ginther et al., 1974, 1976; Mauer et al., 1974) and are significantly correlated with milk fat during the estrous cycle and during early pregnancy (Ginther et al., 1976; Hoffmann and Hamburger, 1973 ; Nuti et al., 1975 ; Pennington et al., 1975). General indications are that the concentration of progesterone is two- to four-fold greater in milk than in plasma. This may be due to its relatively greater solubility in lipid than in aqueous media as compared to the estrogens and cortisol. There is much potential for in vivo storage of progesterone in lipids of the mammary gland and its secretions. McCracken (1964) has shown that concentrations of progesterone in body fat of cows were about fiveto 10-fold of that in plasma. Heap et al. (1975b) have shown that about 80% of administered 3H_progesterone entering milk was found in fat, 19% in casein and 1% in aqueous fractions of milk. A b o u t the same distribution was observed when 3 H-progesterone was added to cow's milk in vitro. Therefore, progesterone may be transferred to milk by simple diffusion from blood and concentrated by absorption into milk fat. Concentrations of progesterone in mammay secretions first exceeded concentrations in plasma 4 to 5 days before calving (figure 1). The ratio of concentrations of progesterone in mammay secretion and blood plasma averaged 1.4 prior to calving, 2.6 in colostrum (0 to 2 days of lactation), and 1.8 for 3 to 25 days of lactation in cows untreated with hormones (group UT). The ratio in mammary secretions 0
Downloaded from https://academic.oup.com/jas/article-abstract/45/3/617/4700693 by guest on 19 November 2018
mone and prolactin, are essential for mammogenesis and onset of lactation (Erb, 1977 for review). However, we know very little about their significance when, after onset of lactation, hormone-containing milk becomes part of the diet for another individual. Therefore, one view could be that hormones excreted in milk have no positive biological function, and that their concentrations in milk represent "imperfect" removal via the venous and lymphatic circulatory systems. The opposite view would be that hormones in milk are biologically important for onset and maintenance of lactation, whether or not they have biological significance when orally ingested. Studies on steroid production rates in vivo and their uptake, metabolism and removal by the mammary gland showed the latter to be a minor route of excretion (Heap and Linzell, 1966; Challis and Linzell, 1973; Heap et aL, 1975a,b; Patterson and Linzell, 1971). Other studies are in general agreement (Lunaas, 1963; Mollett et al., 1976; Monk et al., 1975; Smith et al., 1975; Turner, 1958; Williams, 1962; Willett et al., 1976). Moreover, extent of excretion via milk varies among steroids and mammalian species. In goats, milk contained less than 1% of cortisol removed from blood plasma by the mammary gland (Patterson and Linzell, 1971). Rather, the hormone was returned to the venous circulation. In goats, progesterone taken from blood by the mammary gland was metabolized and the metabolites were removed by the venous route rather than in milk (Heap et al., 1975a). Bovine mammary glands apparently do not synthesize or metabolize progesterone (Heap et al., 1975b). Progesterone excreted via milk represented no more than 3% of the production rate in goats (Heap and Linzell, 1966; Heap et al., 1975a) and cows (Heap et al., 1975b). Mammary uptake of estrone in lactating goats was tess than 3% of the production rate (Challis and Linzell, 1973) but no comparable data on estrogens were found for cows. There is evidence that total estrogen removed daily in milk of cows may be considerably less than 1% of the total metabolized (Monk et al., 1975; Willett et al., 1976) or injected (Mollett et al., 1976). Even though total estrogen excreted in milk is low, concentrations in prepartum mammary secretions and colostrum appear adequate for biological responses when fed to test animals (Turner, 1958 for review). Likewise, it has been demonstrated that synthetic estrogens
ESTROGEN AND PROGESTERONE
/ 61-
r'l MAMMARY SECRETIONS
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DAYS Figure 1. Concentrations of progesterone in mammary secretions and blood plasma from 17 cows prior to (~ 4.9 -+ .2 and 3.6 +- .2 ng/ml; 110 samples) and after calving (2.6 -+ .3 and 1.0 -+ .04 ng/ml; 82 samples). Day 0 was day of calving. Data from Keller et al. (1977).
to 2 days after calving in cows milked prepartum was about one-half (1.7) that observed for cows not milked prepartum (Keller et al., 1977). Larger ratios in cows not milked preparturn probably reflected mammary accumulation of progesterone prior to its decrease in plasma 1 to 2 days before calving. This hypothesis is supported by the observation that concentrations of progesterone in mammary secretions were significantly (P
