Calcitonin produces hypercalcemia in leopard sharks

Area of Science:

• Comparative Endocrinology
• Marine Vertebrate Physiology

Background:

• Calcitonin is a hormone involved in calcium regulation.
• Marine vertebrates, including sharks and bony fish, exhibit unique physiological adaptations.

Purpose of the Study:

• To investigate the physiological effects of calcitonin in marine species.
• To compare calcitonin's action in sharks versus bony fish.

Main Methods:

• Radioimmunoassay (RIA) was used to detect calcitonin in serum.
• Salmon calcitonin was administered to kelp bass and sharks.
• Serum calcium and phosphorus levels were monitored.

Main Results:

• Calcitonin and calcium levels were higher in marine species studied.
• Salmon calcitonin induced hypocalcemia and hypophosphatemia in kelp bass.
• Calcitonin administration resulted in a significant increase in serum calcium (hypercalcemia) in sharks, without affecting phosphorus levels.

Conclusions:

• Calcitonin can induce hypercalcemia in sharks, a novel finding.
• The hypercalcemic effect of calcitonin in sharks does not necessitate a bony skeleton, suggesting a cartilage-mediated mechanism.