Epidermal Growth Factor Regulates Ca ²⁺ Uptake in Primary Cultured Renal Proximal Tubule Cells: Involvement of cAMP, PKC and cPLA ₂

Abstract

Epidermal growth factor (EGF) is known to play an important role in modulating renal transport functions. Thus, we investigated the effect of EGF on Ca²⁺ uptake and its related signals in the primary cultured rabbit renal proximal tubule cells. EGF (50 ng/ml, 1 h) stimulated Ca²⁺ uptake. Its effect was blocked by AG 1478 (an EGF receptor antagonist), genistein or herbimycin A (tyrosine kinase inhibitors). EGF increased intracellular cAMP level and SQ 22536 (an adenylate cyclase inhibitor), Rp-cAMP (a cAMP analogue), or PKI (a protein kinase A inhibitor) blocked the EGF-induced stimulation of Ca²⁺ uptake. EGF-induced stimulation of Ca²⁺ uptake was also blocked by neomycin or U-73122 (phospholipase C inhibitors), staurosporine, H-7, or bisindolylmaleimide I (protein kinase C inhibitors), nifedipine or methoxyverapamil (L-type Ca²⁺ channel blockers). It increased IPs formation by 167 ± 5% compare to control within 90 s. On the other hand, EGF increased [³H]-arachidonic acid release, which was significantly blocked by PKC inhibitors. In addition, PGE₂, one of cyclooxygenase metabolites, and 5,6-EET, one of cytochrome P-450 metabolites, increased Ca²⁺ uptake. These results suggest that cAMP, PLC/PKC, and PLA₂ are involved in EGF-induced stimulation of Ca²⁺ uptake.