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Changes in growth hormone secretion in spontaneously hypertensive rats
E Aguilar1, M L Rodríguez, C Bellido
1Department of Physiology, Faculty of Medicine, Córdoba University, Spain.
Neuroendocrinology
|October 1, 1990
Summary
Spontaneously hypertensive rats exhibit altered growth hormone (GH) levels and responses to growth hormone-releasing factor (GRF). These changes in GH secretion dynamics may contribute to hypertension development.
Area of Science:
- Endocrinology
- Cardiovascular Physiology
- Animal Models of Hypertension
Background:
- Spontaneously hypertensive (SH) rats are a common model for studying human hypertension.
- Growth hormone (GH) plays a role in various physiological processes, and its dysregulation may be linked to cardiovascular conditions.
Purpose of the Study:
- To investigate the secretion of growth hormone (GH) in spontaneously hypertensive (SH) male rats compared to normotensive Wistar-Kyoto (WKY) controls.
- To assess the impact of growth hormone-releasing factor (GRF) on GH release in SH rats.
Main Methods:
- Measurement of plasma GH concentration and pituitary GH content in SH and WKY rats at different ages (30, 60, 90 days).
- In vivo studies involving intravenous injection of GRF into anesthetized SH and WKY rats.
- In vitro studies using hemipituitaries from SH and WKY rats incubated with and without GRF.
Main Results:
- SH rats showed reduced plasma and pituitary GH levels at 30 days old.
- At 60 and 90 days old, SH rats had increased pituitary GH content but normal plasma GH levels.
- In vivo, SH rats exhibited a greater amplitude and duration of response to GRF, while in vitro, they showed higher basal GH release but reduced sensitivity and maximum response to GRF.
Conclusions:
- SH rats display distinct developmental changes in GH secretion, with decreased levels before puberty and altered pituitary content in adulthood.
- The response to GRF in SH rats is complex, showing increased in vivo responsiveness but decreased in vitro sensitivity, suggesting central and peripheral regulatory differences.