Pcl. Hou et Ww. Burggren, CARDIAC-OUTPUT AND PERIPHERAL RESISTANCE DURING LARVAL DEVELOPMENT INTHE ANURAN AMPHIBIAN XENOPUS-LAEVIS, American journal of physiology. Regulatory, integrative and comparative physiology, 38(5), 1995, pp. 1126-1132
Stroke volume (SV) and cardiac output (CO) were measured in anesthetiz
ed larvae of Xenopus laevis from hatching (3 mg) to the end of metamor
phosis (similar to 1 g). CO and SV were calculated from videotaped ima
ges of the intact beating heart; SV increased from 2.4 x 10(-3) mu l a
t 3 mg body mass to 7.6 mu l at 1 g. CO increased from 0.25 mu l/min a
t 3 mg to 623 mu l/min at 1 g. With use of CO, along with arterial pre
ssures from another study [P.-C. L. Hou and W. W. Burggren. Am. J. Phy
siol. 269 (Regulatory Integrative Comp. Physiol. 38): R1120-R1125, 199
5], peripheral resistance and cardiac work were also calculated. Resis
tance decreased rapidly from 701 peripheral resistance units (PRU, mmH
g . s . mm(-3)) at 3 mg body mass to 79 PRU at 20 mg and gradually dec
lined toward 0.9 PRU at 1 g. Cardiac work increased from 0.06 dyn . mm
at 3 mg body mass to 1.27 dyn . mm at 20 mg and then climbed sharply
to 717 dyn . mm at 1 g. The general pattern of change in hemodynamic v
ariables (except heart rate) during larval development-is similar in X
enopus laevis and chick. embryos, suggesting a common pattern for hemo
dynamic development in vertebrate embryos/larvae.