Serum creatine kinase isoenzyme BB in mammalian osteopetrosis

In mammalian osteopetrosis the different mutations exemplify reduced bone r esorption leading to net accumulation of bone. Recently, high blood levels of creatine kinase-BB have been reported in some human forms, suggesting it as a marker of osteopetrosis. In the current study serum creatine kinase-B B was evaluated in relation to known osteoclastic pathophysiology in two hu man types of autosomal dominant osteopetrosis at baseline and after stimula tion with triiodothyronine and in four different rodent mutations. Creatine kinase-BB was increased markedly in Type 2 autosomal dominant osteopetrosi s and in the incisors absent rat, both characterized by large numbers of gi ant osteoclasts, and did not change significantly after stimulation. Althou gh creatine kinase-BB was unchanged in Type 1 autosomal dominant osteopetro sis at baseline and after stimulation, the rodent counterparts characterize d by small osteoclasts, microphthalmic and osteopetrotic mice and toothless rats, had significantly decreased levels. Similar differences were observe d in both types of autosomal dominant osteopetrosis compared with controls concerning tartrate resistant acid phosphatase, Creatine kinase-BB in mamma lian osteopetrosis is related to osteoclastic number and size, where it pro bably reflects the differentiation and maturation of inactive bone resorbin g cells. The isoenzyme does not seem to be a valuable screening marker for osteopetrosis.