Effect of Modulators of Protein Kinase C Activity on Ca²⁺ Transport in Retinal Rod Microsomes

V. P. Emeljanova^*, L. A. Baranova, and I. D. Volotovski

Institute of Photobiology, National Academy of Sciences of Belarus, ul. Akademicheskaya 27, Minsk, 220072 Belarus; fax: (375) (017) 284-2359; E-mail: kabash@biobel.bas.net.by

^* To whom correspondence should be addressed.

Received November 21, 2000; Revision received April 23, 2001

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The effect of modulators of protein kinase C (PKC) activity on Ca²⁺ translocation in retinal rod microsomes was studied. It is shown that PKC activators (phorbol 12-myristate-13-acetate (PMA) and diacylglycerol (DAG)) and inhibitors (chelerythrine chloride, polymyxin B, and phloretin) stimulate and inhibit ATP-dependent Ca²⁺ uptake in retinal rod microsomes, respectively. This effect is apparently due to an influence of PKC on Ca-ATPase contained in these vesicular structures. It was found that PKC inhibitors (chelerythrine chloride, polymyxin B, and phloretin) and activators (PMA and DAG) potentiate Ca²⁺ release from Ca²⁺-loaded retinal rod microsomes. Specific and nonspecific mechanisms of Ca-release stimulation by the modulators of PKC activity are discussed.

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KEY WORDS: retinal rod microsomes, Ca²⁺ transport, phorbol 12-myristate-13-acetate (PMA), 1,2-diacylglycerol (DAG), chelerythrine chloride, polymyxin B, phloretin

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