Effects of protein kinase and phosphatase inhibitors and anti-L antisera on K+ transport in LK sheep red cells

We investigated the role of protein phosphorylation in the action of anti-L on low potassium (LK) sheep red cells. Anti-L stimulated the Na/K pump by four- to fivefold, but Na/K pump activity in anti-L-stimulated or in control cells was unaffected by protein kinase/protein phosphatase (PK/PP) inhibitors. KCl co-transport activity was inhibited by anti-L (about 50%). Co-transport was stimulated by staurosporine; and inhibited by calyculin A, okadaic acid, tyrphostin B46 and genistein; with a similar pattern in both control and anti-L-treated cells. O2 sensitivity of KCl co-transport was similar in control and anti-L-treated cells. Neither control nor anti-L-stimulated Na/K pump activities were O2 sensitive. Incubation with urea stimulated KCl co-transport in both control and anti-L-treated cells. Inhibition of co-transport by anti-L was unaffected by low concentrations of urea but was reduced at higher urea concentrations. Na/K pump activity of control cells was unaffected by incubation with urea, but that in cells stimulated by anti-L was reduced, though not significantly. Under high hydrostatic pressure, KCl co-transport was stimulated, and the inhibitory effects of PP inhibition (okadaic acid), anti-L or combinations of the two were reduced. Results suggest that anti-L does not affect K+ transport in LK sheep red cells via protein phosphorylation.