Source and Regulation of Testosterone Secretion in Pregnant and Pseudopregnant Rats*

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Abstract
Testosterone concentrations were measured in the ovarian, uterine, and jugular venous plasma of pregnant, ordinary pseudopregnant, decidua-bearing, and hysterectomized pseudopregnant rats. Throughout pseudopregnancy and in early pregnancy, testosterone levels in the ovarian vein were approximately 10-fold higher than in either the jugular or the uterine venous plasma. However, while ovarian production of testosterone remained constant through day 18 in decidua-bearing pseudopregnant rats, testosterone secretion by ovaries of pregnant rats dropped to a nadir on day 12. A slight recovery was observed thereafter. However, until day 18, the ovaries produced significantly less testosterone than in the first half of pregnancy. Concomitant to the decline in ovarian production of testosterone was a dramatic rise in uterine secretion of testosterone. Between days 14–22 of pregnancy, testosterone levels in the uterine vein were 4- to 9-fold higher than in the peripheral circulation. In contrast, testosterone concentrations in the uterine vein of pseudopregnant rats with or without decidual tissue were as low as those in the jugular vein. At the end of pseudopregnancy and pregnancy, a sharp increase in ovarian testosterone secretion occurred. Treatment with 0.5 ml LH antiserum induced a drop in the ovarian secretion of testosterone within 24 h in both ordinary and decidua-bearing pseudopregnant rats. In pregnant rats when LH antiserum was administered in early or late pregnancy, a similar decline in ovarian production of testosterone was observed. However in the second half of pregnancy, LH antiserum administration had no effect on ovarian secretion of testosterone. Treatment with 1.5 or 3.0 IU hCG twice a day between days 12–14 of pregnancy induced a dose-dependent increase in the ovarian secretion of testosterone. These results indicate that: 1) throughout pseudopregnancy and in early and late pregnancy, the ovaries secrete significant amounts of testosterone and that the ovarian synthesis of testosterone is dependent on the availability of LH; 2) in the second half of pregnancy (days 13–18), the ovaries secrete only a limited amount of testosterone, while the conceptuses become an important source of testosterone; and 3) the ovarian secretion of testosterone in the second half of pregnancy does not appear to be dependent on LH and could be further stimulated by hCG treatment. (Endocrinology108: 855, 1981)