Figure 7. Effects of electroporation on total Na⁺ content, intracellular Na⁺ content and ⁸⁶Rb⁺ uptake rate in rat soleus muscle.

Isolated muscles in groups of 3 or 4 were placed in polyethylene baskets and incubated at 30 °C in KR buffer. Then the groups of muscles were transferred to an electroporation cuvette containing KR buffer and given three square pulses at 125 V (313 V cm⁻¹) and for a 200 μs duration followed by resting periods lasting from 0 to 15 min. Afterwards they were incubated for 5 min in KR buffer containing ⁸⁶Rb⁺ (0.1 μCi ml⁻¹), blotted and taken for counting of ⁸⁶Rb⁺ activity and determination of Na⁺ content (see Methods for details). In some experiments muscles were preincubated for 75 min in KR buffer containing [¹⁴C]sucrose (0.1 μCi ml⁻¹) and 1 mm unlabelled sucrose before they were transferred to the electroporation cuvette containing KR buffer with the same concentrations of [¹⁴C]sucrose and unlabelled sucrose as in the incubation medium and stimulated 3 times for 200 μs at 125 V (313 V cm⁻¹). Subsequently the muscles were incubated for 5–20 min in KR containing [¹⁴C]sucrose. Each point represents the mean value ± s.e.m. of observations on 4–6 muscles.