Metabolic effects of rectal administration of unmodified eel calcitonin in humans

To evaluate the metabolic effects of unmodified eel calcitonin, nine normal subjects and eleven patients with Paget's disease of the bone entered the study. Eel calcitonin was administered via rectal mucosa at the dosage of 100 and 200 MRCU. Plasma calcium, plasma phosphate and plasma cAMP were measured at a baseline and after 10, 20, 30, 60, 90, 120, 180, 240 min. Rectal administration of 100 MRCU of eel calcitonin decreased plasma calcium and phosphate levels in normal subjects; the hypocalcaemic and hypophosphatemic effects were more marked and statistically significant in Paget's disease patients. Using 200 MRCU of eel calcitonin, statistically significant reductions in plasma calcium levels were observed in controls and in Paget's disease patients. Plasma phosphate decreased after rectal administration of the hormone, but not significantly. A slight but not significant increase in plasma cAMP was observed in normal subjects after the administration of 200 MRCU. These data demonstrate that eel calcitonin administered via rectal mucosa can exert some of the known biologic effects of the peptide.