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Melanin-Concentrating Hormone Stimulates the Release of Luteinizing Hormone-Releasing Hormone and Gonadotropins in the Female Rat Acting at Both Median Eminence and Pituitary Levels
The purpose of this study was to investigate whether melanin-concentrating hormone (MCH) acts directly on the median eminence and on the anterior pituitary of female rats regulating LHRH and gonadotropin release. In addition, immunohistochemistry was used to examine the density and distribution of M...
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Published in: | Biology of reproduction 2001-05, Vol.64 (5), p.1466-1472 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | The purpose of this study was to investigate whether melanin-concentrating hormone (MCH) acts directly on the median eminence
and on the anterior pituitary of female rats regulating LHRH and gonadotropin release. In addition, immunohistochemistry was
used to examine the density and distribution of MCH-immunoreactive fibers in the median eminence of proestrous rats. MCH-immunoreactive
fibers were found in both the internal and external layers of the median eminence and in close association with hypophysial
portal vessels. In the first series of in vitro experiments, median eminences and anterior pituitaries were incubated in Krebs-Ringer
bicarbonate buffer containing two MCH concentrations (10 â10 and 10 â8 M). The lowest MCH concentration (10 â10 M) increased ( P < 0.01) LHRH release only from proestrous median eminences. Anterior pituitaries incubated with both MCH concentrations also
showed that 10 â10 M MCH increased gonadotropin release only from proestrous pituitaries. In the second series of experiments, median eminences
and pituitaries from proestrous rats were incubated with graded concentrations of MCH. MCH (10 â10 and 10 â9 M) increased ( P < 0.01) LHRH release from the median eminence, and only 10 â10 M MCH increased ( P < 0.01) LH and FSH release from the anterior pituitary. The effect of MCH on the stimulation of both gonadotropins from proestrous
pituitaries was similar to the effect produced by LHRH. Simultaneous incubation of pituitaries with MCH and LHRH did not modify
LH but increased the FSH release induced by LHRH. The present results suggest that MCH could be involved in the regulation
of preovulatory gonadotropin secretion. |
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ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod64.5.1466 |