Effects of indomethacin on renomedullary interstitial cells.

The effects of indomethacin, an inhibitor of prostaglandin synthesis, on rat renomedullary interstitial cells were studied. Indomethacin, 5 mg. per kg. intravenously in divided doses over 48 hours, resulted in reduced granularity of interstitial cells (5.56+/-1.37 versus 9.85+/-1.07 granules per cell, (p is less than 0.001) and, at the same time, inhibited the incorporation of 14C-arachidonate into renomedullary phospholipids (715 + 11 versus 1299 + 42 c.pm.per mug. of lipid orthophosphate; p is less than 0.001) 14C-arachidonate incorporation into cortical phospholipids was not affected by indomethacin. There was a close correlation between individual granule counts and 14C-arachidonate incorporation into medullary phospholipids for both control (r=0.85) and indomethacin-treated animals (r=0.9). Radioactivity in the cytosol fraction was depressed by indomethacin reflecting inhibition of prostaglandin synthesis; cytosol radioactivity correlated closely with individual granule count (r=0.81) in the indomethacin-treated but not in the control rats. Indomethacin given as a single dose 4 hours prior to sacrifice resulted in a significant depression of 14C-arachidonate incorporation but did not affect granularity of interstitial cells. The results suggest that granularity of renomedullary interstitial cells reflects the activity of prostaglandin synthesis and the rate of prostaglandin precursor delivery from microsomal phospholipids.