Preliminary evidence for the enterohepatic circulation of progesterone in the pig.

In two gilts, following doses of either 47.7 or 64.6 mumol progesterone, a secondary increase in steroid concentration in portal and mesenteric blood plasma occurred 35-40 min after dosing or 10-15 min after an intravenous (i.v.) dose of cholecystokinin. It is suggested that this increase is splanchnic blood progesterone concentration indicates that the steroid undergoes enterohepatic circulation. In five ovariectomized gilts given single i.v. doses of 47.7 mumol progesterone, the steroid was cleared from the circulating plasma bi-exponentially; the mean half-lives (t 1/2) of the two components were 2.47 (+/- 0.36) and 33.5 (+/- 6.63) min. The t 1/2 of the first component was compatible with the liver being a principal organ of clearance.

Potentiation of growth hormone activity in sheep using monoclonal antibodies.

Monoclonal antibody OA11 was raised against ovine GH; its effects on GH activity were examined in a target species relevant for animal production in vivo. The monoclonal antibody was found to enhance the galactopoietic response to exogenous GH in adult lactating ewes and also to potentiate the diabetogenic activity of both exogenous and endogenous GH in ewe lambs. Thus it was shown that GH activity may be manipulated above its usual dose-response range in normal, intact animals of commercial importance via immunological means.