Dopamine (da) inhibits phosphate transport in opossum kidney (ok) cells through activation of dopamine l (da1) and dopamine 2 (da2) receptors

We have previously demonstrated that DA regulates sodium-dependent phosphate transport in OK cells. The purpose of the present study was to test the hypothesis that DA1 receptors, which are coupled to CAMP, inhibit phosphate uptake in OK cells. Sodium-dependent phosphate transport was measured by uptake of radiolabelled phosphate into OK cell monolayers. The DA1 receptor agonist SKF38393 10JM inhibited phosphate uptake by 29. 5 ±1. 1% while the DA2 receptor agonist quinpirole 105 M inhibited phosphate uptake by 2. 9 ±2%. The DA1 antagonist SCH 23390 10-5 M abolished DA inhibition of phosphate uptake from 12. 4 ±1. 5% to 1. 7 ±2. 2% and blocked DA-stimulated cAMP generation. The DA2 antagonist sulpiride 10-5 M also abolished DA inhibition of phosphate uptake from 12. 4 ± 1. 5% to -1. 2 ±1. 1% but had no effect on DA-stimulated cAMP generation. In the presence of the DA2 antagonist, inhibition of phosphate uptake by SKF 38393 was blunted from 32. 6 ±1. 2% to 21. 5 ±1. 6%. We conclude that DA inhibits phosphate uptake by activation of both DA1 and DA2 receptors. DA1 receptors inhibit phosphate uptake through cAMP generation. The mechanism by which DA2 receptors inhibit phosphate uptake remains unclear.