Peri-OVLT E-series prostaglandins and core temperature do not increase after intravenous IL-1beta in pregnant rats.
Rats have an attenuated febrile response to endogenous pyrogen near the term of pregnancy. Given the fundamental role of E-series prostaglandins (PGEs) in mediating the febrile response to blood-borne endogenous pyrogen, the present experiments were carried out to determine whether PGEs increase in the area surrounding the organum vasculosum laminae terminalis (peri-OVLT) of near-term pregnant (P) rats as in nonpregnant (NP) rats after intravenous (iv) administration of recombinant rat interleukin-1beta (rrIL-1beta). Core temperature was measured by telemetry and peri-OVLT interstitial fluid was sampled in 12 NP and 12 P chronically instrumented, Sprague-Dawley rats by microdialysis for determination of total PGEs by radioimmunoassay. Basal core temperatures were higher in NP compared with P rats (NP 37.9 degrees C +/- 0.5, P 36.9 degrees C +/- 0.4; P < 0.05), but basal peri-OVLT PGEs were similar in both groups (NP 260 +/- 153 pg/ml, P 278 +/- 177 pg/ml; P =not significant). Intravenous administration of rrIL-1beta to NP rats produced a significant increase in core temperature with a latency, magnitude, and duration of 10 min, 0.87 degrees C, and at least 170 min, respectively; peri-OVLT PGEs were increased significantly by 30 min and averaged 270% above basal levels throughout the experiment. In P rats, however, neither core temperature nor peri-OVLT PGEs increased significantly after iv administration of rrIL-1beta. Intravenous administration of vehicle did not significantly alter core temperature or peri-OVLT PGEs in either group of rats. Thus peri-OVLT PGEs do not increase in P rats as they do in NP rats after iv administration of rrIL-1beta. The mechanism of this interesting component of the maternal adaptation to pregnancy, which likely plays a major role in mediating the attenuated febrile response to endogenous pyrogen near the term of pregnancy, warrants further investigation.
Department of Physiology, University of Calgary Health Sciences Centre, Calgary, Alberta, Canada T2N 4N1. fewell@ucalgary.ca
James E
JE
Fewell
Heather L
HL
Eliason
Roland N
RN
Auer
D000818:Animals; D001831:Body Temperature / Q000187:drug effects / Q000276:immunology*; D005260:Female; D007031:Hypothalamus / Q000276:immunology / Q000378:metabolism; D007275:Injections, Intravenous; D007375:Interleukin-1 / Q000494:pharmacology*; D017551:Microdialysis; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000276:immunology*; D011458:Prostaglandins E / Q000378:metabolism*; D011749:Pyrogens / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007375:Interleukin-1; D011458:Prostaglandins E; D011749:Pyrogens