Histamine H₁-receptor-mediated keratan sulfate production in rabbit chondrocytes: Involvement of protein kinase C

We investigated the characteristics of the histamine H₁-receptor in cultured rabbit chondrocytes. Scatchard analysis of [³H]pyrilamine, an H₁-antagonist, binding to the chondrocytes revealed a single class of binding sites with K(D) and B(max) values of 90 ± 12 nM and 56 ± 11 fmol/10⁴ cells, respectively. H₁-agonists stimulated the production of keratan sulfate in a dose-dependent manner. Stimulation of keratan sulfate production was inhibited by pyrilamine. Protein kinase C inhibitors (sphingosine and H-7) also had inhibitory effects. Phorbol 12,13-dibutyrate, a direct activator of protein kinase C, activated the production. When protein kinase C in the chondrocytes was downregulated by preincubation with phorbol ester, the effect of the H₁-agonist on keratan sulfate production was abolished. These results indicate that the histamine H₁-receptor on chondrocytes mediates the accumulation of keratan sulfate production and that protein kinase C is involved in these events.