Protein tyrosine kinase signaling in cold-stimulated contraction of newborn lamb cerebral arteries.

Abstract

We recently reported a contraction of middle cerebral artery (MCA) preparations isolated from newborn lambs in response to tissue cooling. However, the mechanism(s) by which cold stimulus modifies the contractile properties of MCA is not known. We hypothesize that cold stimulus-triggered contraction may be mediated by a signal transduction pathway associated with protein tyrosine kinase (PTK)-dependent machinery. In the present study the tissue bath technique was used to evaluate the effect of select inhibitors of PTK and protein tyrosine phosphatase (PTP) on the temperature-dependent contractile behavior of isolated MCA from new-born lambs. Reduction of tissue bath temperature from 37 to 21 degrees C stimulated contraction (55 +/- 3% of the response to 120 mM KCl). Two distinct inhibitors of PTK, genistein and tyrphostin 47, completely reversed the cold-stimulated contraction, whereas staurosporine, an inhibitor of protein kinase C, was without effect. Sodium orthovanadate (50 microM) potentiated the cold-stimulated contraction, augmenting the slope of the temperature-force relationship over twofold. Two Ser/Thr phosphatase inhibitors (okadaic acid and calyculin A) had no effect on the temperature-force relationship. These results offer experimental evidence to support a novel hypothesis where PTK/PTP-dependent signal transduction pathways may be preferably targeted by cold stimulus and thus provide a biochemical basis for cold-stimulated modification of cerebral vascular contractile properties.