PARATHYROID-HORMONE RELATED PEPTIDE (1-34) AND 1,25-DIHYDROXYVITAMIN D, HAVE NO ADDITIVE EFFECTS ON BONE TARTRATE-RESISTANT ACID-PHOSPHATASE-ACTIVITY IN FETAL-RAT CALVARIA CULTURES
C. Delapiedra et al., PARATHYROID-HORMONE RELATED PEPTIDE (1-34) AND 1,25-DIHYDROXYVITAMIN D, HAVE NO ADDITIVE EFFECTS ON BONE TARTRATE-RESISTANT ACID-PHOSPHATASE-ACTIVITY IN FETAL-RAT CALVARIA CULTURES, Hormone and Metabolic Research, 25(8), 1993, pp. 417-420
Parathyroid hormone related peptide (PTHrP) and 1,25-dihydroxyvitamin
D are known to be resorptive agents which could contribute to the deve
lopment of hypercalcemia in humoral hypercalcemia of malignancy (HHM)
syndrome in Walker 256 tumor bearing rats. In order to clarify some as
pects about the relative contribution of these factors to bone resorpt
ion, we have determined the effects produced by PTHrP (1-34) and/or 1,
25(OH)2D3 on tartrate resistant acid phosphatase (TRAP), a biochemical
marker of bone resorption, in fetal rat calvaria cultures. At the sam
e time, bovine parathyroid hormone (PTH) (1-34) was used as a control
in the experiments in order to compare its effects with those produced
by the other two agonists. In the present work, 10(-7) M PTH (1-34),
10(-7) M PTHrP (1-34) and 10(-8) M or 10(-10) M 1,25(OH)2D3 produced a
significant increase in TRAP activity, when these agonists were added
to the calvaria culture. Surprisingly, and in spite of the different
ways of action of PTH, PTHrP and 1,25(OH)2D3, their actions are not ad
ditive in our experiment. The results of the present work suggest that
any of the two implicated factors PTHrP or 1,25(OH)2D3 could be indiv
idually responsible for the high rate of bone resorption that takes pl
ace in HHM syndrome in Walker 256 carcinosarcoma bearing rats, althoug
h other different agents, like TGF, could also be implicated.