The effect of parathyroid hormone on the numbers of nuclei in feline osteoclasts in vivo.

Twelve kittens aged 18 weeks each received a single injection via a femoral vein; eight were given 4 USP units PTE per kg body weight and four were given an equivalent amount of normal saline. Four PTE and four saline (control) animals were killed after 1 hour and four PTE kittens were killed after 6 hours. Fresh imprints of femoral metaphyseal bone were stained by histochemical methods for succinate, malate, betahydroxy butyrate and glutamate dehydrogenases. These preparations were similar and the unstained nuclei contrasted sharply with the background stained cytoplasm, making possible accurate nucleus counts. Cumulative frequency distribution for control and PTE 1 hour osteoclasts samples were similar asymmetric curves with a positive skew with no statistically significant difference between them. chi2 analyses did, however reveal a statistically highly significant (P < 0.0001) difference between PTE 6 hours osteoclasts and both untreated and PTE 1 hour samples. The arithmetic mean and median numbers of nuclei increased 6 hours after administration of PTE. The results suggest that in kittens an early response of osteolcasts to PTE in vivo is an increase in the numbers of contained nuclei.