Hormonal regulation of acid phosphatase release by osteoclasts disaggregated from neonatal rat bone

Osteoclasts disaggregated from neonatal rat long bones and incubated on plastic or glass substrates were found to release a considerable proportion of tartrate-resistant acid phosphatase into culture supernatants. Enzyme release was detectable in the supernatant medium of cultures containing as few as ten cells after 1 hr of incubation and proceeded in a linear manner for the ensuing 6 hr. Calcitonin (1 pg/ml) and cytochalasin B (5 micrograms/ml) inhibited release into the supernatant, suggesting that release represents enzyme secretion. Prostaglandin E1 induced transient inhibition followed by recovery; parathyroid hormone and 1,25(OH)2 vitamin D3 were without influence. Acid phosphatase release in these cultures shows a pattern of hormone responsiveness that coincides with the effects of these hormones on bone resorption by isolated osteoclasts. The extent of acid phosphatase release and its regulation by calciotropic hormones imply a central role for acid hydrolase secretion in osteoclastic bone resorption. The experimental system described in this study may facilitate analysis of the pharmacological hormonal and cellular regulation of osteoclastic function.