In vitro activation of adenylate cyclase by parathyroid hormone and calcitonin during normal and hydrocortisoneinduced cleft palate development in the golden hamster

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Abstract
An adenylate cyclase highly responsive to stimulation by parathyroid hormone (PTH) and calcitonin (CT) in vitro was observed at certain times during normal prenatal development of the maxillary‐palatal process complex in the golden hamster. Responses of the enzyme to these hormones were barely detectible at the earliest stage examined (day 10/20). The enzyme became extremely sensitive to activation by either hormone during the time of rapid growth of the palatal processes (day 11/20) and during fusion between the palatal processes (day 12/20). Thereafter, responses were greatly diminished and little or no activation of adenylate cyclase was observed until birth. Adenylate cyclase from fetuses in which clefts of the secondary palate were induced by maternal treatment with hydrocortisone (50 mg) on day 11/3 also displayed an enhanced sensitivity to PTH and CT on day 11/20, but the sensitivity of the enzyme was greatly decreased from that in normal animals during the normal time of palatal fusion (day 12/20) and was barely detectible or absent at the remaining time periods studied (days 13/20 and 14/20). Addition of hydrocortisone to the incubation mixture, either separately or in combination with PTH or CT, did not remarkably affect the response of adenylate cyclase to these hormones. Moreover, the appearance of the adenylate cyclase sensitive to hormonal activation did not result from changes in phosphodiesterase activity during palatal maturation.