Showing papers by "Anunciación Lafuente published in 1996"
TL;DR: The existence of an interrelationship between elevated circulating Prolactin levels and CsA, which probably takes place at the hypothalamic level, to regulate the pulsatile pattern of prolactin secretion in male rats, is suggested, although a direct effect of the drug on the ectopic gland in pituitary-grafted male rats cannot be excluded.
8 citations
TL;DR: Data suggest that CsA modifies the pulsatile secretory pattern of prolactin in pituitary-grafted male rats.
Abstract: The interrelationship between the effects of prolactin and cyclosporine (CsA) appears to be very complex and until now poorly understood. The aim of the present work was to analyze whether chronic treatment with CsA could modify the episodic secretion of prolactin in male rats and whether the presence of an ectopic pituitary could counteract the effects of the drug on the pulsatile secretion pattern of this hormone. At 30 days of age, male rats were implanted with one anterior pituitary under the kidney capsule or where sham-operated. Both pituitary-grafted and sham-operated rats were injected sc for 30 days with the vehicle or CsA (5 mg/kg/day), beginning on the day of surgery. Pituitary grafting and/or CsA administration changed the pulsatile secretion pattern of prolactin. In pituitary-grafted male rats, mean serum prolactin levels, absolute pulse amplitude, and half-life of the hormone increased, while the pulse frequency decreased, compared with the values found in sham-operated rats. CsA administration to sham-operated rats increased the relative amplitude of prolactin peaks and diminished the half-life of the hormone, compared with rats of the same group treated with vehicle. However, CsA treatment in pituitary grafted rats led to lower mean serum prolactin levels and absolute amplitude, while the frequency, duration, and relative amplitude of prolactin pulses were not modified. Plasma prolactin levels did not change in control animals, whereas a reduction in circulating values of the hormone was found in pituitary grafted animals. These data suggest that CsA modifies the pulsatile secretory pattern of prolactin in pituitary-grafted male rats. The different effects observed in the control and pituitary-grafted animals might be due to a direct effect of the drug on the ectopic lactotrophs that are submitted to local regulatory influences different from those of the in situ pituitary which are submitted to the regulatory influence of the hypothalamus.
8 citations
6 citations
Journal Article•
TL;DR: The data suggest that CyA differentially affect the release of pituitary hormones and that there is an interrelationship between previously high plasma prolactin levels and CyA to modulate pituitARY hormone secretion.
Abstract: The effects of cyclosporine (CyA) on pituitary hormone secretion in animals with previously high plasma prolactin levels have been studied. Hyperprolactinemia was either induced in 30 day old male rats by the transplantation of one anterior pituitary gland from a litter mate donor or they were sham-operated to be used as controls. Both pituitary-grafted and sham-operated animals were injected s.c. with the vehicle or CyA (5 mg/kg weight per day) for 10 days, beginning 30 days after surgery. As expected, pituitary grafting markedly increased plasma prolactin levels as compared with the values found in control animals. Hyperprolactinemia was associated with reduced plasma LH and GH levels, increased plasma TSH levels and with no changes in circulating FSH levels. CyA administration to control animals increased plasma prolactin and TSH levels, decreased plasma levels of LH and did not modify circulating values of FSH and GH. Furthermore, CyA administration to pituitary-grafted animals decreased plasma prolactin and TSH levels, whereas plasma concentrations of GH and gonadotropins did not change. These data suggest that CyA differentially affect the release of pituitary hormones and that there is an interrelationship between previously high plasma prolactin levels and CyA to modulate pituitary hormone secretion.
3 citations
TL;DR: The data suggest that CyA may modify the effects induced by prolactin on pituitary hormone secretion, although direct effects of the drug on the hypothalamic-pituitary axis cannot be excluded, according to the data obtained in sham-operated rats.
1 citations
1 citations
TL;DR: Study of the pulsatile pattern of the hormone after the administration of the neuropeptide suggests that LHRH significantly suppressed pulsatile prolactin secretion, and that this effect was blunted by exposure to previously elevated circulating prolactins.
Abstract: Regulation of prolactin secretion involves complex interactions of multiple inhibitory and stimulatory factors. Among them, luteinizing hormone-releasing hormone (LHRH) has been shown, when analyzed in single samples, to exert both stimulatory and inhibitory influences on prolactin secretion. In the present study, we have further examined the effects of LHRH on prolactin secretion by studying the pulsatile pattern of the hormone after the administration of the neuropeptide. For this purpose, adult sham-operated and pituitary-grafted female rats, exhibiting diestrus smears were bled for 3 hr during the morning (1030 to 1330 hr). Two pulses of LHRH (10 ng/kg body wt) were administered 60 and 120 min after starting the bleeding period. Pituitary grafting increased the mean serum prolactin levels, absolute amplitude of the hormone peaks, and its mean half-life, compared with control animals. In sham-operated rats, LHRH administration diminished mean serum prolactin levels, the absolute pulse amplitude and frequency of prolactin peaks. In pituitary-grafted animals, LHRH administration only decreased the pulse frequency of prolactin peaks. These data suggest that LHRH significantly suppressed pulsatile prolactin secretion, and that this effect was blunted by exposure to previously elevated circulating prolactin levels.
1 citations