We studied the effects of beta-adrenergic stimulation on the formation
of adenosine 3',5'-cyclic monophosphate (cAMP) and on the cell volume
in Rana ridibunda red blood cells under O-2 (high oxygen atmosphere)
and under N-2 (hypoxia) gases. Adrenergic stimulation caused the accum
ulation of cAMP and the swelling of R. ridibunda erythrocytes. 10(-5)
M adrenaline and 10(-5) M isoproterenol seem to be the more efficient
concentration in causing greater cell swelling. The amount of cAMP req
uired for adrenergic swelling was minimal; swelling was observed at cA
MP concentrations higher than 20 nM. Maximal swelling was seen when th
e cellular cAMP concentration reached 40 nM at high oxygen atmosphere.
Isoproterenol caused a greater increase in water content than adrenal
ine. At hypoxic conditions the water content and cAMP concentrations o
btained after stimulation with adrenaline and isoproterenol were great
er than at high oxygen atmosphere. Since the adrenergic response seems
to be blocked both by prazosin and propranolole the adrenoreceptors o
f R. ridibunda red cells may be classified as alpha(1)- and beta-recep
tors. The enhancement of cAMP and cell swelling may be either due to a
n increase in the number of adrenoreceptors, or to increased responsiv
eness of the erythrocyte Na+-H+ antiporter to catecholamines during hy
poxia. These responses are believed to enhance blood oxygen transport
during periods of increased oxygen demands. (C) 1996 Wiley-Liss, Inc.