Changes in intercellular electrical coupling of smooth muscle accompanying atrophy and hypertrophy

Longitudinal tissue impedance was determined for cat circular intestinal muscle that was either hypertrophied due to volume overloading or atrophied due to defunctionalization. These conditions were produced by bypassing 50 cm of jejuno-ileum in six cats and, 2-6 mo later, removing segments from the proximal jejunum of the hypertrophied functional gut and from the atrophied proximal end of the bypassed loop. Impedances were compared with those of jejunal circular muscle from 15 normal cats. Specific tissue impedance was determined by a modification of the method of Tomita (J. Physiol. Lond. 201: 145-159, 1969), which employs Krebs and Krebs-sucrose solutions; a tissue shrinkage of 5%, empirically found to occur in Krebs-sucrose solution, was corrected for. Impedance values were determined at 20 frequencies between 30 Hz and 30 kHz. The value at 30 kHz was taken to represent the specific myoplasmic resistance (Rmyo) of each tissue, while the difference between the value of 30 Hz and 30 kHz was taken to represent the specific junctional resistance (Rj). Values (in omega X cm) for Rmyo were control 134 +/- 2, functional 128 +/- 5, bypassed 151 +/- 6 (mean of means +/- SE). Corresponding values for Rj were control 173 +/- 15, functional 96 +/- 27, bypassed 340 +/- 75. Calculated values (in microF/cm) for junctional capacitance were control 2.66, functional 6.10, bypassed 1.97. Acid uncoupling by saturating the bathing solutions with 100% CO2 revealed a pH-sensitive resistive component of Rj, assumed to be attributable to gap junctions.(ABSTRACT TRUNCATED AT 250 WORDS)