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Growth hormone secretion after hypophysial stalk transection in pigs
Summary
Hypophysial stalk transection in gilts reduced episodic growth hormone (GH) secretion and increased basal GH levels, indicating the hypothalamus regulates GH release patterns and basal inhibition in pigs.
Area of Science:
- Endocrinology
- Neuroendocrinology
- Reproductive Biology
Background:
- Growth hormone (GH) secretion is tightly regulated by hypothalamic factors.
- The role of the hypothalamus in modulating GH secretion patterns, particularly basal levels, requires further elucidation in swine models.
Purpose of the Study:
- To investigate the impact of severing the hypophysial stalk on GH secretion patterns in mature ovariectomized gilts.
- To determine the necessity of hypothalamic control for both episodic and basal GH secretion in pigs.
Main Methods:
- Ovariectomized gilts underwent hypophysial stalk transection or sham operation, with a nylon disk preventing regeneration.
- Blood samples were collected at frequent intervals before and after surgery to measure serum GH concentrations.
Main Results:
- Hypophysial stalk transection did not alter mean overall serum GH concentrations compared to presurgical levels or controls.
- Episodic GH secretion was significantly dampened following hypophysial stalk transection.
- Basal GH blood concentrations were elevated in transected gilts relative to presurgical levels and controls.
Conclusions:
- GH synthesis and secretion persist in gilts even without direct hypothalamic neural input.
- The hypothalamus is essential for regulating the episodic release of GH.
- The hypothalamus plays a critical role in the tonic inhibition of basal GH secretion in pigs.