Immunoreactive erythropoietin studies in hypoxic rats and the role of the salivary glands.
Rat erythropoietin (Ep) cross-reacts in the radioimmunoassay (RIA) for human Ep developed in this laboratory. Immunoreactive Ep was measured in serum and tissues of male rats in response to short-term hypoxia (0.43 atm for 24 h). In the unstimulated rat all tissues examined had low levels of Ep, with the exception of the submaxillary or salivary gland (SG). Exposure to hypoxia for 24 h resulted in significant increases in kidney and serum levels of Ep, with no apparent change in SG content. Sialectomy immediately prior to exposure reduced renal Ep production and serum levels significantly after 4 h of exposure. Nephrectomy (N) confirmed previous results by others: Ep production after exposure to hypoxia was reduced but not abolished. The effect of N plus sialectomy was identical to that of N alone, thus excluding the SG as a source of extrarenal Ep in nephrectomized rats. The long-term effect of SG ablation to the same constant stimulus was a steady decline of the Ep response during the first week after surgery, both in renal production and serum levels. Thereafter, from one to six weeks the serum levels remained constant, being higher than in the unstimulated rat but significantly lower than in intact hypoxic animals. No cross-reactivity in the RIA was found with renin, renin substrate, nerve and epidermal growth factor, or somatomedins. If this Ep-like substance in the SG were the source of extrarenal Ep, it should have been possible to document an increase in serum concentration before an increase could be measured in renal content. It appears, however, that the presence of the SG is necessary for renal tissue to be able to synthesize Ep during hypoxia.
D000818:Animals; D004921:Erythropoietin / Q000378:metabolism*; D000860:Hypoxia / Q000503:physiopathology*; D007158:Immunologic Techniques; D007668:Kidney / Q000378:metabolism*; D008297:Male; D051381:Rats; D012469:Salivary Glands / Q000378:metabolism*; D014018:Tissue Distribution
D004921:Erythropoietin