ALTERED FREE CALCIUM TRANSIENTS IN PIG-KIDNEY CELLS (LLC-PK(1)) CULTURED WITH PENICILLIN STREPTOMYCIN/

The effect of a conventional antibiotic penicillin/streptomycin) mixtu re on the widely used kidney epithelial cell line, LLC-PK1, as investi gated by measuring growth and intracellular free calcium. Free calcium concentration was the same in cells cultured for 3 to 7 wk with (''pl us'') and without (''minus'') antibiotics both at rest and when challe nged with high (14 mM) external calcium. When exposed to vasopressin, minus cells exhibited significantly smaller calcium transients than pl us cells. A similar difference existed for transients elicited by a ca lcium ionophore, 4-br-A23187. After longer periods of culture (>20 wk) , minus cells grew slower than plus cells but on reaching confluence ( minus cells took 1 day longer) the morphologies and viabilities were i ndistinguishable. The finding that culture with pinicillin/streptomyci n reversibly modified some properties of LLC-PK1 cells, at least partl y through altered calcium homeostasis, is of importance for workers us ing this cell model to study drug effects and raises the general possi bility of similar effects on other cultured cells.