Parathyroid hormone bioassay using human kidney cortical cells in primary culture.

The biological activity of parathyroid hormone (PTH) has been investigated by measuring intracellular accumulation of cyclic AMP (cAMP) in human kidney cortical cultures. Enzyme dispersed cortical cells from non-invaded kidney poles of patients undergoing nephrectomy for cancer were used after 5 days of primary culture. Bovine PTH (1-84) produced a significant increase of cAMP accumulation in cultured cells at a dose (53.7 ng/ml) 10-fold lower than that found for the minimal stimulatory effect when using preparations of human purified plasma membranes. The action of bovine PTH (1-84) was very rapid, a response was detected after 5 min and a ceiling effect after 30 min. Cortical cells showed a slightly lower sensitivity to synthetic bovine PTH (1-34) (half maximal increase dose: 0.66 microgram/ml), compared to bovine PTH (1-84) (half maximal increase dose: 0.32 microgram/ml), but revealed a higher sensitivity to human PTH purified from the medium of parathyroid cell cultures (half maximal increase dose: 11.2 ng/ml). Arginine-vasopressin (AVP) also increased the cAMP accumulation of kidney cortical cultured cells, with a potency and efficacy lower than that of human 'culture' PTH, while in kidney medullary cells in primary culture AVP exerted a strong response and the effect of PTH was poor or absent. Calcitonin and glucagon were weak stimulators of kidney cortical cell cAMP accumulation.