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Hypercalcemic effect of insulin in the chick.
Endocrinology
|June 1, 1979
Summary
Insulin significantly increases plasma calcium levels in young chicks, even at low doses. This effect occurs independently of vitamin D and suggests a novel mechanism for calcium regulation in birds.
Area of Science:
- Endocrinology
- Comparative Physiology
- Mineral Metabolism
Background:
- Conflicting reports exist regarding insulin's effect on plasma calcium (Ca) in rats.
- Birds exhibit high sensitivity to parathyroid hormone and resistance to insulin's hypoglycemic effects.
Purpose of the Study:
- To investigate the impact of insulin on plasma Ca concentration in 10-day-old chicks.
- To explore potential mechanisms underlying insulin's effect on calcium homeostasis in avian models.
Main Methods:
- Administration of commercial bovine and purified porcine insulin to chicks.
- Measurement of plasma Ca and phosphate concentrations at 60 minutes post-injection.
- Dose-response studies with insulin, parathyroid hormone, and 1 alpha-hydroxyvitamin D3.
- Assessment of insulin's effect under propranolol treatment and vitamin D deprivation.
Main Results:
- Both insulin types induced a dose-related elevation in plasma Ca.
- Hypercalcemia was observed even at a low insulin dose (0.05 U) without affecting plasma phosphate.
- Insulin and parathyroid hormone showed similar dose-response curve slopes for calcium elevation.
- Propranolol alone also elevated plasma Ca; vitamin D status did not influence insulin's hypercalcemic effect.
Conclusions:
- Insulin administration raises plasma calcium concentration in chicks.
- The mechanism of insulin-induced hypercalcemia in chicks remains to be elucidated.
- This finding suggests a distinct role for insulin in avian calcium regulation compared to mammals.