Effects of parathyroid hormone on bone acid hydrolases in tissue culture.

Abstract

Experiments were carried out to assess the activity of acid hydrolases of bone cells under in vitro conditions. Rat and mouse skull bones were kept in vitro for 2 to 6 days in the presence and absence of added parathyroid hormone. The activities of acid protease (cathepsin D), acid phosphatase, and β-glucuronidase were measured in the culture media and in homogenates prepared from the cultured bones. All three enzymes showed increased activity in various degrees in the media when parathyroid hormone (PTE) was present, but increased enzyme synthesis in the homogenates could be detected only in the case of acid protease and acid phosphatase. The acid protease showed maximum activity at pH 3.0–3.2, and the PTE-stimulated increase was time-dependent. Lysozyme incorporated into the culture medium stimulated acid protease activity, while histone had an opposite effect. Cultures kept in incomplete media for a limited period of time also responded to PTE treatment with an increased release of acid hydrolases into the medium.