Cardiac output, heart rate, and blood pressure as influenced by equi-antiarrhythmic doses of eight antifibrillatory agents

Effects of the local anesthetics brufacain and lidocaine on transmembrane action potentials, refractory period, and reactivation of the sodium system in guinea pig heart muscle

Lidocaine (3-10(-5) and 10(-4) M) and equimolar concentrations of brufacain dose-dependently reduced the depolarization velocity (dV/dtmax) and the force of contraction of guinea pig atria and papillary muscles. Repolarization time was increased in atria but reduced in papillary muscles. The maximum effects on action potential parameters were identical but developed with brufacain more slowly than with lidocaine. In papillary muscles lidocaine (3-10(-5) M) prolonged the functional refractory period. No such effect but even a shortening was observed with brufacain. As brufacain reduced the duration of the action potential (AP) more than the functional refractory period, the "relative refractory period" (in percent of AP duration) was slightly prolonged. The half-time of the recovery of the Na+ system was increased three to five times the control value after lidocaine but only doubled after brufacain.

[Differentiation of the effect of diuretic urine extracts on the renal medullary blood flow (author's transl)]

In sodium depleted rats urine extracts of hydrated healthy human volunteer cause an increase in water excretion of 52% (p less than 0.005) and in sodium excretion of 45% (p less than 0.005). Cardiac output of the volumen loaded rats increases from 465 +/- 104 ml to 528 +/- 128 ml/kg-min (p=n.s.). Rb86 is used as an indicator for renal hemodynamics. Compared with controls there is an increase in blood flow through the outer medulla from 1.57 +/- 0.65 to 2.28 +/- 0.61 ml/g-min, through the inner medulla from 0.75 +/- 0.30 to 1.01 +/- 0.30 ml/g-min, and through the papillary tips from 0.85 +/- 0.04 ml to 1.21 +/- 0.25 ml/g-min. The experiments show that the diuretic/natriuretic urine extracts influence the hemodynamics of the renal medulla.However, since the significance level of the enhanced medullary blood flow is only low (p less than 0.1) it is impossible to find out the direct site of action of the urine extracts.

Seasonal variations of cardiac output in rats

Cardiac output of rats shows seasonal variations with low values in spring and summer and high ones in autumn and winter. The stroke volume was much more implicated in these changes than the heart rate. The seasonal changes of cardiac output are probably due to changes of thyroid function.