Catecholamines and ascorbic acid as stimulators of bovine ovarian oxytocin secretion

Abstract

The effects of catecholamines and ascorbic acid on cultured bovine granulosa cells have been examined to assess their possible role in the initiation and maintenance of luteal oxytocin secretion. The actions of these agents have also been compared with the previously reported ability of follicular theca tissue to enhance oxytocin secretion. Using granulosa cells cultured in serum-supplemented medium, we observed a highly significant enhancement of oxytocin secretion in the presence of adrenaline and noradrenaline, particularly over the concentration range 1-10 mumol/l. This effect was accompanied by smaller and less consistent changes in progesterone secretion and did not involve any change in the time-course of oxytocin secretion. Acetylcholine was without effect. Ascorbic acid stimulated oxytocin secretion when used alone over a range of concentrations, but was also able to synergize with adrenaline. Lactic acid was ineffective. The stimulation of oxytocin secretion by adrenaline could be blocked by equimolar propranolol, but the stimulation of progesterone was not blocked. Propranolol had a variable effect on the ability of theca tissue to stimulate oxytocin secretion by granulosa cells but the results also suggested the presence of some beta-agonistic activity in the culture medium. We conclude, first, that catecholamines may be involved in the regulation of ovarian oxytocin secretion, secondly, that ascorbate may regulate oxytocin secretion through its involvement in the biosynthesis of oxytocin but also through interaction with catecholamines and, thirdly, that the stimulatory action of theca tissue probably does not involve the action of beta-agonists.

Concentrations of catecholamines, ascorbic acid, progesterone and oxytocin in the corpora lutea of cyclic and pregnant cattle

“…The origin of DA in bovine CL is not clear. Battista et al [3] and Denning-Kendall et al [6] [24] provide evidence for the involvement of ascorbic acid in the stimulation of progesterone synthesis and OT secretion from bovine granulosa cells in vitro [25]. Thus, maximal luteal and follicular function was associated with increased concentrations of total ascorbate within the tissue in pigs [30] and in cattle [26], although its precise role in steroidogenesis has not been established [22].…”

Local Release of Progesterone and Oxytocin from Microdialyzed Corpus Luteum in Superovulated Ewes: Characterization during the Non-breeding Season.

“…Such assumption is substantiated by the findings showing innervation of the normal bovine CL with adrenergic [25][26][27][28][29][30][31] as well as peptidergic nerves [32]. It would be possible that an episodic influence of innervation exist at any period of the experiment, but the high secretory activity of the CL up to Days 12-13 may mask such a basic function, and a direct influence may appear only after a decrease in the CL capacity to secrete P.…”

L-Ascorbic acid (vitamin C) supplementation to optimize health and reproduction in cattle

“…It also acts as a reducing agent for the synthesis of aldosterone in the adrenal gland (Yanagibashi et al 1990) and oxytocin in granulosa cells of corpus luteum (Luck and Jungclas 1988). Vitamin C regulates oxytocin secretion through direct interaction with catecholamines (Luck and Jungclas 1987). In humans, vitamin C is required for the biosynthesis of carnitine and the catecholamines that regulate the nervous system (Iqbal et al 2004).…”