Involvement of beta-adrenoceptors in the regulation of luteal function in cattle.

The infusion of beta-adrenomimetic drug (bamethan sulphate--BS) on day 11 of the oestrous cycle markedly increased peripheral progesterone concentration whereas infusion of beta-antagonist (propranolol) decreased plasma progesterone levels in heifers. Oxytocin injected on days 2-6 of the oestrous cycle shortened the length of the cycle (to 7-9 days) whereas the length of the cycle in heifers injected with oxytocin followed by injections of either BS or xanthinol (theophylline nicotinate--a potent vasodilatory drug) was normal (21.8 +/- 1.7). Heifers injected with BS on days 13-21 of the oestrous cycle had increased levels of progesterone on days 13-19 of the cycle and the length of the cycle was normal (22.3 +/- 0.6 compared with 21.3 +/- 1.5 for the control). The data indicate that: (1) beta-adrenergic stimulation overcomes the action of oxytocin given on days 2-6 of the cycle, whereas the stimulation of beta-receptors on days 13-21 of the oestrous cycle raised progesterone plasma concentration but did not prevent spontaneous luteolysis. (2) Basal secretion of progesterone in cattle is partly dependent on constant beta-adrenergic stimulation.