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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Hypotonic swelling stimulates L-type Ca²⁺ channel activity in vascular smooth muscle cells through PKC

¹Department of Anatomy, Physiology, and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, Alabama 36849; and ²Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306

Submitted 2 December 2003 ; accepted in final form 29 March 2004

It has been suggested that L-type Ca²⁺ channels play an important role in cell swelling-induced vasoconstriction. However, there is no direct evidence that Ca²⁺ channels in vascular smooth muscle are modulated by cell swelling. We tested the hypothesis that L-type Ca²⁺ channels in rabbit portal vein myocytes are modulated by hypotonic cell swelling via protein kinase activation. Ba²⁺ currents (I_Ba) through L-type Ca²⁺ channels were recorded in smooth muscle cells freshly isolated from rabbit portal vein with the conventional whole cell patch-clamp technique. Superfusion of cells with hypotonic solution reversibly enhanced Ca²⁺ channel activity but did not alter the voltage-dependent characteristics of Ca²⁺ channels. Bath application of selective inhibitors of protein kinase C (PKC), Ro-31–8425 or Go-6983, prevented I_Ba enhancement by hypotonic swelling, whereas the specific protein kinase A (PKA) inhibitor KT-5720 had no effect. Bath application of phorbol 12,13-dibutyrate (PDBu) significantly increased I_Ba under isotonic conditions and prevented current stimulation by hypotonic swelling. However, PDBu did not have any effect on I_Ba when cells were first exposed to hypotonic solution. Furthermore, downregulation of endogenous PKC by overnight treatment of cells with PDBu prevented current enhancement by hypotonic swelling. These data suggest that hypotonic cell swelling can enhance Ca²⁺ channel activity in rabbit portal vein smooth muscle cells through activation of PKC.

cell swelling; protein kinases; calcium current

This article has been cited by other articles:

				B. Callaghan, J. Zhong, and K. D. Keef Signaling pathway underlying stimulation of L-type Ca2+ channels in rabbit portal vein myocytes by recombinant Gbeta{gamma} subunits Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2541 - H2546. [Abstract] [Full Text] [PDF]