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      In vitro and in vivo Growth Hormone Responsiveness to Growth Hormone-Releasing Factor in Male and Female Zucker Rats

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          Abstract

          In order to determine whether there is an anomaly in the pituitary responsiveness to growth hormone (GH)-releasing factor in the genetically obese rat, we examined the in vitro and in vivo effects of rGRF(1–29)NH2 (GRF) on GH release in male and female Zucker rats. The effect of increasing GRF concentrations (1.56, 6.25, 12.5, 25 and 50 p M) was first tested on GH release from freshly perifused anterior pituitary cells. In both sexes, the GH response per one pituitary equivalent to each GRF concentration tested was reduced in the obese group. However, when GH release was expressed as a percent of initial cell GH content, there was no difference between the lean and the obese groups. Furthermore, under pentobarbital anesthesia, GRF was injected intravenously at two consecutive doses of 0.8 and 4.0 µg/kg body weight in obese and lean animals. In both sexes, the GH response to each dose of GRF tested was decreased in the obese group. Basal serum GH concentrations were similar in male and female obese rats compared to their respective lean siblings. In conclusion, this study demonstrates a decrease of the in vitro and in vivo pituitary response to GRF in the obese Zucker rat, suggesting a possible secondary defect at the pituitary level.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1989
          1989
          02 April 2008
          : 50
          : 4
          : 454-459
          Affiliations
          Neuroendocrinology Laboratory, Notre-Dame Hospital Research Center, and University of Montreal, Montreal, Canada
          Article
          125262 Neuroendocrinology 1989;50:454–459
          10.1159/000125262
          2510049
          © 1989 S. Karger AG, Basel

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          Page count
          Pages: 6
          Categories
          Original Paper

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