The calcemic response to PTH in the rat: effect of elevated PTH levels and uremia.
Secondary hyperparathyroidism (2 degrees HPT) is a consistent finding in renal failure. A decreased calcemic response (CR) to parathyroid hormone (PTH) contributes to the development of 2 degrees HPT. Since parathyroidectomy (PTX) corrects the decreased CR to PTH in azotemic animals, down-regulation of PTH receptors induced by an elevation of PTH has been advanced as an important factor in the development of 2 degrees HPT. The goal of the study was to determine in azotemic rats whether a progressive reduction of PTH improves the CR to PTH and whether the maintenance of normal PTH levels corrects the CR to PTH. Seven groups of pair-fed rats were studied. Three groups of rats had normal renal function (NRF groups) and received either a high phosphorus (HPD-NRF), a moderate phosphorus (MPD-NRF), or a low phosphorus (LPD-NRF) diet. Three azotemic (NX) groups received similar diets (HPD-NX, MPD-NX and LPD-NX groups) in order to vary the magnitude of 2 degrees HPT. A PTX was performed in a fourth azotemic group (PTX-NX) to induce the complete absence of PTH. After 14 to 16 days on the maintenance diets, the CR to PTH was determined with a 48 hour infusion of 1-34 rat PTH.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Medicine, Wadsworth VAMC, Los Angeles, California.
J
J
Bover
A
A
Jara
P
P
Trinidad
M
M
Rodriguez
A
A
Martin-Malo
A J
AJ
Felsenfeld
D000818:Animals; D002118:Calcium / Q000097:blood*; D015536:Down-Regulation; D006962:Hyperparathyroidism, Secondary / Q000097:blood* / Q000503:physiopathology; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000503:physiopathology; D008297:Male; D010280:Parathyroid Glands / Q000502:physiology; D010281:Parathyroid Hormone / Q000097:blood*; D016105:Parathyroidectomy; D016226:Phosphorus, Dietary / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D014511:Uremia / Q000097:blood* / Q000503:physiopathology
D010281:Parathyroid Hormone; D016226:Phosphorus, Dietary; D002118:Calcium