Immunohistochemistry for leptin in adipose tissue. Rats injected with saline solution, lactic acid or LS were euthanized 48 hr after injections and the retroperitoneal adipose tissue was fixed in formalin immediately after euthanasia. Cytoplasmic immunostaining for leptin (*) was stronger in adipocytes in LS-injected animals (B) than in corresponding adipocytes of rats injected with saline (A). Light counterstain with hematoxylin. Magnification × 400.