Summary. Incubation of bovine luteal cells with the alternative pathway catecholamines octopamine, synephrine and deoxyadrenaline at concentrations of 10 −6 to 10−3 m enhanced the production of progesterone (P < 0·05). Tryamine did not alter basal progesterone production (P > 0·05). Addition of noradrenaline and adrenaline at concentrations of 10−4 to 10−7 m significantly elevated the production of progesterone (P < 0·05). The steroidogenic response to noradrenaline and adrenaline was greater than that for octopamine, synephrine and deoxyadrenaline (P < 0·05). Response to both primary (10−6 m) and alternative (10−4 m) pathway catecholamines was inhibited by propranolol (10−5 m, P < 0·05) but not phentolamine (10−5 m, P > 0·05). These results demonstrate that octopamine, synephrine and deoxyadrenaline can affect steroidogenesis by bovine luteal cells, and their action is mediated by β-adrenergic receptors.
P. J. Battista and W. A. Condon
P. J. Battista and W. A. Condon
Summary. The addition of acetylcholine or histamine (10− 7 to 10−4 m), γ-aminobutyric acid, a dopamine agonist, and melatonin (10−7 to 10−5 m) did not alter basal or LH-stimulated progesterone production (P>0.05). The addition of the specific β2-adrenergic agonist terbutaline and salbutamol did not significantly elevate progesterone production. Treatment of luteal cells with serotonin (5-HT), 10−6 to 10−4 m, increased the production of progesterone (P<0.05). This stimulated production was inhibited by the addition of mianserin (10−5 m, a 5-HT antagonist; P<0.05). Isoproterenol (10−7 to (10−4 m) also resulted in significant increases in progesterone production (P<0.05). The combined treatments of 5-HT + LH, isoproterenol+ LH, or isoproterenol + 5-HT did not result in a further increase in progesterone above that observed in response to LH or isoproterenol alone (P>0.05). The isoproterenol-induced progesterone production could not be blocked by butoxamine (10−5 m, a β2-antagonist), or practolol (10−5 m, a β1-antagonist), but was inhibited by propranolol (10−5 m, a general β-antagonist; P<0.05). The response to isoproterenol was unaffected by mianserin (10−5 m). These results demonstrate a possible role for 5-HT in the regulation of steroidogenesis by the corpus luteum of the cow. Furthermore, these results suggest that serotonin-induced progesterone production is a receptor-mediated event.
P. J. Battista, J. P. Poff, D. R. Deaver, and W. A. Condon
Summary. Biogenic amines were administered using osmotic pumps placed subcutaneously in the neck region of regularly cycling, non-lactating dairy cows on Days 9–11 (oestrus = Day 0) of the oestrous cycle. Blood samples were collected using indwelling jugular catheters and the plasma progesterone concentrations were measured. Samples were collected at 4-h intervals for the first 12 h of treatment and thereafter at 12-h intervals for the remainder of the 72-h treatment period. After administration of various doses of noradrenalne, adrenaline and serotonin (0·5–2·0 μg/kg/h) significant elevation of plasma progesterone was achieved at a dosage of 2·0 μg/kg/h (P < 0·01). The response to adrenaline was greater than that observed for noradrenaline and serotonin (P < 0·05). Within-treatment comparison to pretreatment samples showed plasma progesterone concentrations to increase within 4 h after the administration of noradrenaline, adrenaline and serotonin (P < 0·05) and this enhancement was maintained throughout the treatment period (P < 0·05). The elevation in plasma progesterone concentrations induced by noradrenaline, adrenaline and serotonin was independent of changes in circulating concentrations of luteinizing hormone. These results support a physiological role for endogenous biogenic amines in the control of bovine luteal progesterone production.