Adenosine uptake and [3H]nitrobenzylthioinosine binding in developing rat brain.
The ontogenesis of adenosine transport sites as labelled with [3H]nitrobenzylthioinosine ([3H]NBI) was examined using radioligand binding and membrane preparations from whole brain and 4 brain regions of rats between the postnatal ages of one day through to adulthood. In whole brain, cerebral cortex and cerebellum, [3H]NBI binding was two-fold higher in 6-day-old than in 50-day-old rats. In contrast, [3H]NBI binding was higher in adults than in one-day-old rats by 4-fold in hypothalamus and 8-fold in superior colliculus. In cortex and hypothalamus, the levels of [3H]NBI binding in newborn and adult rats were reflected by changes in Bmax and not Kd values. As a measure of the utility of [3H]NBI as a probe for identifying functional adenosine transport sites, we examined [3H]NBI binding to and [3H]adenosine accumulation by intact brain cells prepared from adult and newborn rats. For [3H]NBI binding to brain cells from adult rats, the values of Kd were 0.092 nM and of Bmax were 274 fmol/mg protein. For newborns, slightly higher Kd and Bmax values were observed; 0.2 nM and 395 fmol/mg protein, respectively. [3H]Adenosine accumulation was higher in brain cells from one-day-old than from adult rat brains. Kinetically this uptake was best described by a two-component model: the Vmax values for the high- and low-affinity uptake, and the Km value for the high-affinity component in one-day-old rats were greater than in adults.(ABSTRACT TRUNCATED AT 250 WORDS)
Geiger
J D
JD
Department of Pharmacology and Therapeutics, University of Manitoba, Faculty of Medicine, Winnipeg, Canada.
D000241:Adenosine / Q000378:metabolism*; D000375:Aging / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000254:growth & development / Q000378:metabolism*; D002531:Cerebellum / Q000254:growth & development / Q000378:metabolism; D002540:Cerebral Cortex / Q000254:growth & development / Q000378:metabolism; D007031:Hypothalamus / Q000254:growth & development / Q000378:metabolism; D007288:Inosine / Q000031:analogs & derivatives*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013477:Superior Colliculi / Q000254:growth & development / Q000378:metabolism; D013868:Thioinosine / Q000031:analogs & derivatives* / Q000378:metabolism
D013868:Thioinosine; D007288:Inosine; C001789:4-nitrobenzylthioinosine; D000241:Adenosine