Phosphorylation in coronary artery cold-induced contraction in the newborn lamb

Myocardial dysfunction alter hypothermic protection has been linked to various mechanisms. Coronary vasospasmin particular may be responsible for ischemic injury during reperfusion. Herein we hypothesized that coronary arteries (CA) sustain a cold-induced contraction during hypothermia mediated by a protein tyrosine kinase (PTK)-/protein tyrosine phosphatase (PTP)-dependent pathway. isolated newborn lamb CA rings were studied in a tissue bath for isometric contraction during 2-h profound (17 degreesC) or ultra-profound (7 degreesC), hypothermia. in parallel, protein tyrosine phosphorylation was evaluated by use of the Western blot technique. Na-orthovanadate (SOV) and genestein (GEN) were used separately and in combination to evaluate the effect of PTK/PTP activation on CA contraction and tyrosine phosphorylation during cooling (17 or 7 degreesC) vs 37 degreesC. Cooling from 37 to 7 degreesC induced transient contraction at similar to 17 degreesC (29% KCI response), which was more prominent during rewarming to 37 degreesC (36% KCI). Cooling to 17 degreesC resulted in sustained contraction 17-10% KCI,. which was reversible upon rewarming. Cold-induced contraction was significantly enhanced by SOV (7- to 10-fold at 17 degreesC: 2-fold at 7 degreesC) and abolished by GEN. Concurrently, tyrosine phosphorylation of 33-, 45-, and 104-kDa proteins increased during cooling (35-100% at 17 degreesC: 46-66% at 7 degreesC). Tyrosine phosphorylation was similarly enhanced by SOV (1.7- to 2.3-fold at 17 degreesC: 2.9- to 3.9-fold at 7 degreesC) and abolished by GEN in the presence or absence of SOV. These results support a prominent role for the PTK/PTP signal transduction pathway in the: coronary artery cold-induced contraction. This information provides one possible biomolecular mechanism linked to ischemia/reperfusion pathophysiology of CA in neonatal hearts exposed to hypothermic myocardial protection. (C) 2001 Academic Press.