Spleen emptying and venous hematocrit in humans during exercise.
The spleen may release pooled erythrocytes to the general circulation during strenuous conditions such as heavy exercise. Most of our knowledge of this reservoir function of the spleen derives from animal studies, and the splenic contribution to the circulating blood volume in humans has been regarded as unimportant. We recorded the erythrocyte content in the human spleen during graded bicycle exercise to maximal working capacity. In five normal adults 99mTc-labeled autologous erythrocytes were injected intravenously, and the subjects were placed on bicycles with the back against a gamma camera focusing on the spleen. During increasing exercise the splenic erythrocyte content decreased linearly, and at maximal work load it had been reduced to a mean of 34.2% (range 44-26%) of the initial count rate at supine rest. Concomitantly norepinephrine and epinephrine in plasma increased gradually, whereas neuropeptide Y increased only at maximal exercise. A rise in hematocrit from a mean of 44.6 to 48 was observed, but the autotransfusion of erythrocytes from the spleen only partly explains the rise in hematocrit during physical activity.
Department of Clinical Physiology and Nuclear Medicine, Herlev Hospital, University of Copenhagen, Denmark.
M
M
Laub
K
K
Hvid-Jacobsen
P
P
Hovind
I L
IL
Kanstrup
N J
NJ
Christensen
S L
SL
Nielsen
D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D004837:Epinephrine / Q000097:blood; D016552:Ergometry; D004912:Erythrocytes / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006400:Hematocrit; D006439:Hemodynamics / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009478:Neuropeptide Y / Q000276:immunology / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D011877:Radionuclide Imaging; D012039:Regional Blood Flow / Q000502:physiology; D013670:Sodium Pertechnetate Tc 99m; D013154:Spleen / Q000098:blood supply* / Q000000981:diagnostic imaging
D006454:Hemoglobins; D009478:Neuropeptide Y; D013670:Sodium Pertechnetate Tc 99m; D009638:Norepinephrine; D004837:Epinephrine