A theoretical description of arterial pressure-flow relationships with verification in the isolated hindlimb of the dog

We developed and tested a new two-compartment serial model of the arterial vasculature which unifies the capacitance (downstream arterial compliance) and waterfall (constant downstream pressure load) theories of blood flow through the arteries. In this model, blood drains from an upstream compliance through a resistance into a downstream compliance which empties into the veins through a downstream resistance which terminates in a constant pressure load. Using transient arterial pressure data obtained from an isolated canine hindlimb preparation, we tested this model, using a stop-flow technique. Numerical parameter estimation techniques were used to estimate the physiologic parameters of the model. The downstream compliance was found to be more than ten times larger than the upstream compliance and the constant pressure load was significantly above venous pressures but decreased in response to vasodilation. Our results support the applicability of both the capacitance and waterfall theories.     

Heterogeneity in the response to histamine of isolated dog arteries

Arterial rings were used to evaluate the differences in the effect of histamine (HIS) on canine dorsal pedal (DPA) and coronary arteries. Moreover, the responses of intact coronary arteries (IA) to HIS were compared with those of arteries isolated from sham operated dogs (SA) and from dogs in the late postinfarction period (PA). DPA responded to HIS added cumulatively with contraction which was potentiated by cimetidine (CIM) and reversed by mepyramine (MEP). IA responded with relaxation potentiated by MEP and reversed by CIM. Under resting conditions, coronary arteries responded to a single concentration of HIS with contraction or relaxation (in IA, SA). In PA, only contractions were seen. Responses of PA were significantly higher than those of IA and SA. It appears that in PA the ratio of H₁- and H₂-receptors is changed.     

Effect of histamine on microvasculature of isolated dog gracilis muscle.

Isogravimetric capillary pressure (Pci), capillary filtration coefficient (CFC), and plasma protein concentration were measured before and during adminisistration of histamine in an isolated, independently perfused canine gracilis muscle. Histamine produced an average decrease in Pci of 14.1 mmHg, an increase in CFC of 36-fold, and an increased rate of plasma protein escape of at least 24-fold. These results suggest that histamine reduces the reflection coefficient for protein at the capillary wall and are consistent with predictions of the theory of restricted diffusion assuming that 1-2.5% of available pores increase in radious from 40 to 240 A.     

Effects of norepinephrine and histamine on vascular resistance in isolated perfused mouse liver

Mice have frequently been used for a variety of physiological studies because of the development of genetic engineering. However, the characteristics of hepatic vessels such as the vascular resistance distribution and the reactivity to various vasoconstrictors are not known in mice. We therefore determined the basal levels of segmental vascular resistances and the effects of histamine and norepinephrine on the vascular resistance distribution of mice. The liver of male non-inbred ddY mice was excised and perfused via the portal vein with 5% bovine albumin-Krebs solution at a constant flow rate. The sinusoidal pressure was measured by the double occlusion pressure and used to determine the presinusoidal (R(pre)) and postsinusoidal (R(post)) resistances. The basal R(post) comprised 53 +/- 1% of the total hepatic vascular resistance. The norepinephrine and histamine increased R(pre) in a greater magnitude than R(post) with liver weight loss. However, the response to histamine was weaker than that to norepinephrine. Moreover, histamine-induced vasoconstriction showed tachyphylaxis. In conclusion, the presinusoidal and postsinusoidal resistances of mouse livers were similar in magnitude. The presinusoidal vessels predominantly contract in response to norepinephrine and histamine in mouse livers.     

Ionic composition of arterial and mixed venous plasma in the unanesthetized dog.

The use of permanent catheters in the aorta and pulmonary artery permitted the establishment of normal values for hemoglobin concentration in blood and -or pH, PCO2, osmolality, and protein and electrolyte concentrations in the plasma of arterial and venous samples from unanesthetized, undisturbed dogs, and the comparison of the ionic composition of simultaneously taken arterial and venous samples. Arterial samples yielded the following mean values: CHb, 143 g liter-1; pHP, 7.427; PCO2, 32.5 mmHg; CPosmol, 295 mmol kg-1; CPpr, 73.1 g liter-1, CPNa+, 148.0; CPK+, 3.9; CPCa2+, 2.38; CPMg2+, 0.85; CPCl-, 116.0; CPHCO3-, 21.1; CPlact-, 1.4; CPphosph, 1.21; net cation equivalency, 16.4; and anion gap, 1.03 mmol liter-1 in eight male mongrel dogs with seven or eight samplings from each dog. The anion gap in arterial and venous plasma was small, indicating that the contribution of sulfate and organic acids to the ionic composition of dog plasma is quantitatively unimportant. In simultaneously taken arterial and venous samples the following significant arteriovenous differences were found: HP, +0.038; PCO2, -5.6 mmHg; CPosmol, -1.8 mmol kg-1; protein, -0.8 g liter-1; CPNa+, -1.0; CPK+, -0.1; CPCl-, +1.3; and CPHCO3-, -1.7 mmol liter-1. These differences are explained on the basis of the changes that occur in blood upon the addition of CO2 and the ensuing chloride and water shifts.