Altered basal and adenosine-mediated protein flux from coronary arterioles isolated from exercise-trained pigs

Solute flux per unit surface area and concentration gradient, (J(S)/SdeltaC), was quantified in arterioles isolated from hearts of sedentary (SED) and exercise-trained (EX) female Yucatan Miniature Swine. Apparent permeability (P(S)) was assessed from measures of J(S)/SdeltaC for two proteins, alpha-lactalbumin (alpha-lact) and porcine serum albumin (PSA), under basal conditions and following 5 min suffusion with 10(-5) M adenosine (ADO). Both proteins were labelled with the fluorescent dye tetramethyl rhodamine isothiocyanate. Basal P(S) to alpha-lact differed with exercise training ((P(S)alpha-lact)SED = 5.2+/-1.8 (median+/-median absolute deviation (MAD), n = 9 pigs) versus (P(S)alpha-lact)EX = 7.4+/-1.1 x 10(-7) cm s(-1), n = 9, P < 0.05). For the larger protein PSA, basal P(S) did not change with training (P(S)PSA)SED = 50+/-1.6, N = 11 vs. (P(S)PSA)EX = 4.1+/-1.2 x 10(-7) cm s(-1), N = 11). Suffusion of the arterioles (33+/-4 microm diameter, n = 18 vessels) from SED hearts (n = 14) with 10(-5) M ADO decreased P(S)alpha-lact 15+/-8% relative to control and was without effect on P(S)PSA. By contrast, in arterioles (39+/-4 microm diameter, n = 22 vessels) from EX hearts (n = 14), ADO increased P(S)alpha-lact and P(S)PSA by 32 and 65% respectively, indicating that receptor-mediated changes in permeability were also sensitive to exercise training. These data demonstrate that, for coronary arterioles, permeability to macromolecules adapts to exercise training. The adaptive mechanisms may involve more than one structural component of the vessel wall as the changes in permeability were size-dependent.