Localization of thyroid hormone in subpopulations of rat alveolar macrophages.

Radioimmunoassay and immunocytochemical staining methods were used to study the distribution of thyroid hormone in rat alveolar macrophages. The cells were fractionated into six subpopulations by Percoll density gradient. Positive immunoreactive tri-iodothyronine (T3) was observed in all subpopulations of macrophages, especially in low-density (1.040 and 1.050 g cm-3) groups, by avidin-biotin-peroxidase immunostaining techniques. The macrophages also showed various patterns of cellular T3 stainability. Results from radioimmunoassay of macrophage extracts also demonstrated that macrophages of low density had a higher level of total T3 than those of higher densities (greater than or equal to 1.060 g cm-3).