Cyclic nucleotides and the rapid inhibitions of bone 45Ca uptake in response to bovine parathyroid hormone and 16,16-dimethyl prostaglandin E2 in chicks.
Intravenous injection of chicks with bovine parathyroid hormone (1-34) (3.3 micrograms/100 g body wt.) or 16,16-dimethyl PGE2 (5 micrograms/100 g body wt.) caused rapid (3 minute) net inhibition of 45Ca uptake into femur and calvarium. These agents also elevated bone adenosine 3',5'-cyclic monophosphate (cAMP) but not guanosine 3',5'-cyclic monophosphate (cGMP) levels at this time. Methylxanthine phosphodiesterase inhibitors (MXPI), caffeine, theophylline, and 3-isobutyl-1-methylxanthine (IBMX) (0.3-5 mg/100 g body wt.) similarly inhibited net 45Ca uptake into femur and to a lesser extent calvarium. Plasma 45Ca and total Ca levels were unaltered or showed a slight tendency to be increased over control values 3 minutes after injection. However, the effects of the non-MXPI, dibutyryl-cAMP (0.5-5 mg/100 g body wt.) on bone 45Ca uptake were negligible. Of the MXPI, only IBMX elevated total cAMP levels in chick bone at 3 minutes. These data implicate but do not confirm a mediatory role for cAMP in the rapid inhibitory actions of PTH and PGEs on bone net 45Ca uptake in chicks.
Shaw
A J
AJ
School of Pharmacy and Biomedical Sciences, Portsmouth Polytechnic, UK.
Dacke
C G
CG
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015064:16,16-Dimethylprostaglandin E2 / Q000494:pharmacology*; D000818:Animals; D001842:Bone and Bones / Q000032:analysis / Q000502:physiology*; D003994:Bucladesine / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D002645:Chickens / Q000502:physiology*; D000242:Cyclic AMP / Q000032:analysis; D008297:Male; D009712:Nucleotides, Cyclic / Q000502:physiology*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011459:Prostaglandins E, Synthetic / Q000494:pharmacology*; D013806:Theophylline / Q000494:pharmacology
D002132:Calcium Radioisotopes; D009712:Nucleotides, Cyclic; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011459:Prostaglandins E, Synthetic; C025076:parathyroid hormone (1-34), bovine; D002110:Caffeine; D003994:Bucladesine; D013806:Theophylline; D000242:Cyclic AMP; D015064:16,16-Dimethylprostaglandin E2; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine