Microsphere and dilution techniques for the determination of blood flows and volumes in conscious mice

Although the mouse is the most commonly used transgenic species, little is known regarding cardiovascular and fluid homeostasis in this animal. Therefore, the reference microsphere and dilution techniques were adapted for the measurement of cardiac output (CO), regional blood flows, and intravascular fluid volumes in the conscious mouse. Previously acclimatized C3H mice were studied 4-5 h after surgery and recovery from anesthesia. Approximately 40,000 85Sr-labeled microspheres were injected into the left ventricle while a reference sample was withdrawn at one of two rates from the femoral artery. 51Cr and 125I were used for the determination of blood volume (BV), plasma volume (PV), and Fcells ratio (whole body hematocrit/large vessel hematocrit). CO and BV in the conscious mouse were 16 +/- 1.4 ml/min and 2.3 +/- 0.1 ml, respectively. Anesthesia lowered heart rate, blood pressure, PV, and altered the distribution of CO. Two successive injections of 15,000-20,000 microspheres were tolerated in the mouse without an increase in total peripheral resistance. The results indicate that the microsphere and indicator dilution techniques can be applied to study cardiovascular and fluid homeostasis in the mouse.

Distortion of calculated whole-body hematocrit during lower-body immersion in water

We found a difference between the venous hematocrits of immersed and nonimmersed arms during immersion of the lower body in cold water but not during a comparable exposure to warm water. Fourteen healthy men were exposed to three different experimental conditions: arm immersion, body immersion, and control. The men always sat upright while both upper extremities hung vertically at their sides. During arm immersion, one forearm was completely immersed for 30 min in either cold water (28 degrees C, n = 7) or warm water (38 degrees C, n = 7). This cold-warm water protocol was repeated on separate days for exposure to the remaining conditions of body immersion (immersion of 1 forearm and all tissues below the xiphoid process) and control (no immersion). Blood samples were simultaneously drawn from cannulated veins in both antecubital fossae. Hematocrit difference (Hct diff) was measured by subtracting the nonimmersed forearm's hematocrit (Hct dry) from the immersed forearm's hematocrit (Hct wet). Hct diff was approximately zero when the men were exposed to the control condition and body immersion in warm water. In the remaining conditions, Hct wet dropped below Hct dry (P less than 0.01, 3-way analysis of variance). The decrements of Hct diff showed there were differences between venous hematocrits in immersed and nonimmersed regions of the body, indicating that changes of the whole-body hematocrit cannot be calculated from a large-vessel hematocrit soon after immersing the lower body in cold water.

Apparent escape rate of RIHSA and 51Cr-labeled erythrocytes from the blood of volume-expanded rats

The disappearance rate constant of radioiodinated human serum albumin (RIHSA) and 51Cr-tagged erythrocytes was measured in rats before and after intravenous, isoncotic blood volume expansion (6% bovine albumin; 75 or 33% of blood volume). Before volume expansion the average slope of the semilogarithmically plotted plasma RIHSA activity was -2.068 X 10(-3) +/- 0.146 X 10(-3) (SE) min-1. The slope was not significantly changed when tested by subsequent tracer injections which were made immediately after and 1 h after volume expansion. Preinfusion plasma volume (PV) was constant, but total erythrocyte volume (RCV) increased at a significant rate from 0.0253 +/- 0.0030 to 0.0300 +/- 0.0038 ml/g body wt over the 2-h period. PV was elevated and RCV was unchanged by the infusion, but both decreased significantly thereafter. The observed erythrocyte loss could not be accounted for by sampling or bleeding. Arterial hematocrit remained constant while RCV and PV were decreasing, and it was identical to whole-body hematocrit throughout. It was concluded that 1) isoncotic albumin expansion did not change the rate constant of transcapillary albumin loss; 2) nonsteady state PV could be calculated from a single preinfusion RIHSA dose; and 3) sequestration of blood may be a part of the rat's response to volume expansion.

Effect of Age, Sex, and Egg Laying on the Total Erythrocyte Volume (51CrO4 Label) and the Plasma Volume (125I-Serum Albumin Label) of Japanese Quail

In a study carried out to assess the effect of age, sex, and egg laying on the true Mood volume in Japanese quail by the simultaneous determination of the 51Cr erythrocyte volume and the 125I plasma volume, the mean values in milliliters per kilogram body weight for true blood volume, plasma volume, and erythrocyte volume in young unsexed quail, adult males, adult nonlaying hens, and laying quail, respectively, were 83.2, 59.1, 24.1; 74.2, 47.3, 26.9; 67.6, 42.9, 24.7; and 71.2, 47.3, and 23.8. Young birds had higher plasma volume and true blood volume and lower whole body hematocrit and Fcells ratio than the adults. The erythrocyte volume of young quail was not significantly different from that of the nonlaying hens but was less than that of adult males. Adult males had higher plasma volume, erythrocyte volume, and true blood volume than nonlaying hens. A comparison between the layers and nonlayers showed that the layers had a higher plasma volume and Fcells ratio and a lower whole body hematocrit than the adult nonlayers.