Quantitative evaluation of gap junctions during development of the brown adipose tissue.

Gap junctions of rat brown adipose tissue (BAT) were studied with the freeze-fracture technique during development. The frequency and the mean area of gap junctions increased after birth, reached a maximal development during the functional phase of the tissue (birth to 3--4 weeks) and decreased while brown adipose tissue's function regressed (from 3--4 weeks on). Gap junctional area per cell volume, an indirect estimate of intercellular coupling, followed closely the phases of BAT activity, suggesting an involvement of these junctions in the functioning of brown adipose tissue.