Involvement of β-adrenoceptors in the regulation of luteal function in cattle

Abstract

The infusion of β-adrenomimetic drug (bamethan sulphate—BS) on day 11 of the oestrous cycle markedly increased peripheral progesterone concentration whereas infusion of β-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. (1) β-adrenergic stimulation overcomes the action of oxytocin given on days 2–6 of the cycle, whereas the stimulation of β -receptors on days 13–21 of the oestrous cycle raised progesterone plasma concentration but did not prevent spontaneous luteolysis. 2. (2) Basal secretion of progesterone in cattle is partly dependent on constant β-adrenergic stimulation.