Interaction of transcapillary Starling forces in the isolated dog forelimb

Abstract

Three of the four Starling forces were measured in the intact dog forelimb after anesthetization and all four of the Starling forces were measured in the same forelimb which was surgically isolated yet innervated. In the isolated forelimb, isogravimetric capillary pressure (Pci) averaged 15.6 mmHg; colloid osmotic pressure of the plasma proteins (IIp) averaged 19.9 mmHg; mean interstitial fluid pressure (Pif) was +0.4 mmHg, and the average value of interstitial colloid osmotic pressure (IIif) was 4.9 mmHg. Thus the net imbalance in the Starling forces, i.e., (Pci - Pif) - (IIp - IIif), averaged 0.3 mmHg. Furthermore, the value of IIif was consistently decreased after isolation (average decrease of 1.2 mmHg) while Pif was always increased following isolation (average increase of 4.3 mmHg). In addition, it was found that if the forelimb was denervated during isolation, then Pif was increased by an average of 2 mmHg above Pif in the innervated, isolated forelimb. In summary, these studies show that the differences between the intact and isolated forelimb are that Pci averages 10-11 mmHg in the intact forelimb and 15-16 mmHg in the isolated innervated forelimb while interstitial fluid pressure is negative in the intact limb and positive in the isolated limb.