USE OF ADVERSE CONDITIONS TO STIMULATE A CELLULAR STRESS-RESPONSE BY EQUINE ARTICULAR CHONDROCYTES

Objective - To determine the response of equine articular cartilage ce lls to heat and calcium stresses. Design - Analysis of newly synthesiz ed, [S-35]methionine-labeled proteins after treatment of isolated prim ary equine chondrocytes. Procedure - Primary cultures of equine articu lar chondrocytes were incubated at temperatures ranging from 37 to 42 C for hear stress experiments or incubated in the presence or absence of the intracellular calcium pump inhibitor, thapsigargin, for calcium stress experiments. Patterns of new protein synthesis were determined by incubating with [S-35]methionine followed by separation oi protein s by use of one- or two-dimensional gel electrophoresis and visualizat ion of labeled proteins by use of fluorography. Results - Equine chond rocytes cultured at temperature of 42 C had increased synthesis of spe cific protein, compared with the profile of protein synthesis in contr ol chondrocytes cultured at 37 C. These changes were characteristic of the heat shock stress response described in a number of other mammali an cell-types. Equine chondrocytes cultured in the presence of thapsig argin also had increased synthesis of specific proteins. Two-dimension al gel electrophoresis of these newly synthesized proteins revealed th e changes to be consistent with the induction oi the glucose-regulated protein family oi stress proteins. Conclusions - Changes in the patte rn of new protein synthesis can be induced in differentiated equine ar ticular chondrocytes by heal shock or calcium stress. These responses are characteristic of a widely described mammalian stress response tha t has been postulated to be involved in cellular protective mechanisms . The ability of equine chondrocytes to mount a robust stress response may be important in the processes of tissue damage and recovery in ar ticular joints of horses.