In Vivo and In Vitro effects of a cyclopropenoid fatty acid on progesterone synthesis by the ovine corpus luteum

Graduation date: 1991Two experiments were conducted to examine the effect of\ud a cyclopropenoid fatty acid on luteal cell function. In Exp.\ud 1, 12 mature ewes were mated to a fertile ram, assigned to two\ud groups (n = 6/group) and laparotomized on day 18 of gestation.\ud Ewes with corpora lutea (CL) in both ovaries were unilaterally\ud ovariectomized while ewes with a CL in one ovary only were\ud allowed to remain intact. An extract of Sterculia foetida\ud seeds (1.09 mg), consisting of a mixture of fatty acid methyl\ud esters including 750 ug of sterculic acid (SA), or 1.09 mg\ud oleic acid methyl ester (OA) was injected into the artery\ud supplying the ovary bearing CL. Jugular blood was collected\ud on day 18 before surgery and daily thereafter until day 30 of\ud gestation or until detected estrus, whichever occurred first.\ud Sera were assayed for progesterone (P₄) by radioimmunoassay.\ud In Exp. 2, 12 mature ewes were laparotomized on day 10 of the\ud estrous cycle and CL were removed, weighed and sliced for\ud incubation. Corpora lutea from two ewes were pooled for each\ud incubation. Slices of CL were preincubated in medium\ud containing 145 ng/ml of S. foetida extract (100 ng/ml\ud sterculic acid methyl ester) or 145 ng/ml oleic acid methyl\ud ester (control) for 90 min. Then, slices of tissue were\ud washed and reincubated in fresh medium containing 25 ug 22(R)-\ud hydroxycholesterol/ml (0.079 nM final concentration) or 25 ug\ud 5-pregnen-3βol-20-one/m1 (0.084 nM final concentration) for\ud 120 min. Tissue plus medium were analyzed for P₄. Injection\ud of SA or OA on day 18 of gestation caused a reduction in serum\ud concentrations of P4 within 24 h, after which concentrations\ud of steroid remained low and relatively constant in control and\ud those SA-treated ewes that remained pregnant until day 30 of\ud gestation. Three of six ewes that were injected with SA\ud exhibited estrus within 3 to 5 days after treatment. Serum\ud concentrations of P₄ of SA-treated ewes differed from those of\ud OA-injected control ewes (P<0.01). Luteal tissue subjected\ud to SA or OA in vitro did not differ in ability to synthesize\ud P₄ during subsequent incubation in the absence of precursor\ud substrate (incubated controls). Relative to respective\ud incubated controls, P₄ synthesis by tissue previously exposed\ud to SA or OA was not altered by incubation in the presence of\ud 22(R)-hydroxycholesterol. Presence of 5-pregnen-3βol-20-one\ud (pregnenolone) in the medium significantly increased P₄\ud synthesis by luteal tissue preincubated with SA or OA compared\ud with that of controls. However, response of SA-treated tissue\ud was markedly less than that of tissue exposed to OA (P