Uptake of erythrocyte-associated component of blood testosterone and corticosterone to rat brain.
To study transport of steroids by erythrocytes, the tissue uptake of erythrocyte-associated testosterone and corticosterone was studied in vivo using a single injection technique into the carotid artery of rats. A brain uptake index (BUI) was calculated by dividing the ratio of [3H]steroid to [14C]butanol (internal reference) in the brain tissue by that in the injection material, and multiplying by 100%. BUIs of testosterone and corticosterone in an erythrocyte suspension were 131 +/- 3% (mean +/- SE, n = 6) and 57.0 +/- 2.7% (n = 6), respectively, which were greater than those in buffer (100 +/- 4%; n = 4, P less than 0.01 and 39.8 +/- 4.6%; n = 4, P less than 0.01, respectively). The erythrocyte accounted for 83.9% and 76.7% of the total testosterone and corticosterone delivered to the tissues, respectively, when calculated on the assumption that the BUIs of steroid in buffer and in the supernatant of an erythrocyte suspension are the same. BUIs of corticosterone in hemolysate and in a suspension of erythrocyte plasma membranes (60.8 +/- 7.0%; n = 4 and 69.5 +/- 3.7%; n = 4, respectively) were also greater than those in buffer (P less than 0.05 and P less than 0.01, respectively). Our results suggest that the erythrocyte-associated component of testosterone and corticosterone are delivered to the tissue of rat brain, and that their membranes may play a major role in their capacity to transport steroids to the tissues.
Hiramatsu
R
R
Third Department of Internal Medicine, Kumamoto University Medical School, Japan.
Nisula
B C
BC
D000818:Animals; D001692:Biological Transport; D001921:Brain / Q000378:metabolism*; D003345:Corticosterone / Q000097:blood / Q000378:metabolism*; D004912:Erythrocytes / Q000737:chemistry*; D008297:Male; D051381:Rats; D013739:Testosterone / Q000097:blood / Q000378:metabolism*
D013739:Testosterone; D003345:Corticosterone