STIMULATION OF IN VITRO RELEASE OF CALCITONIN FROM RAT AND HUMAN C-CELLS BY CIMETIDINE

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Abstract
Previous reports have suggested that the H2-receptor blocker,.cimetidine, can inhibit parathyroid hormone (PTH) release. The present studies were designed in an attempt to see whether cimetidine affects secretion of calcitonin (CT) as well. Entire thyroparathyroid glands from 8-day-old baby rats or small pieces of a human medullary thyroid carcinoma were incubated at 37C for up to 8 h in chemically defined culture medium gassed with 95% 02–5% CO2- With rat thyroparathyroids, both CT and PTH released into medium were measured using RIAs that detect the rat hormones. CT secreted from human Ccells was measured using an RIA for human CT. The results were: (A) As we had found previously, cimetidine at doses of 3 × 10-3 M and 9 × 10-3M inhibited PTH release from rat thyroparathyroids by as much as 50–60% (p–5M cimetidine released considerably more CT than tissue incubated in control medium (48 ± 9.3 vs 21 ± 3.6 ng CT/μg tissue protein, p2 receptors and whether it is of any physiological significance awaits clarification.