Expression of adenylyl cyclase isoforms in articular chondrocytes of rat

Chondrocytes exhibit a life cycle of proliferation, differentiation, maturation, and apoptosis; rate of each of these processes is dependent on the expression of temporal and spatial signals. Identification of these signals is essential to understand the molecular basis of chondrocyte physiology. Ca²⁺ and cAMP are second messengers involved in signal transduction cascade. Adenylyl cyclase (AC) is an integral membrane protein that catalyzes the synthesis of cAMP from ATP. In this study we have employed immunohistochemical technique to study expression of AC isoforms in articular chondrocytes. Our results show that AC isoforms I, II, III, IV and V/VI are differentially expressed in articular chondrocytes of the shoulder, elbow, hip, and knee joints. The significance of these findings and the role of expressed isoforms in physiology of articular chondrocytes are discussed.