Cytochemistry for lectins, actin, nucleotide tetrazolium reductases and several phosphatases in the porcine semitendinosus muscle: vascular development in young pigs.

An ontogeny study of the porcine semitendinosus muscle was conducted to meet two objectives: 1) to evaluate enzyme histochemistry, lectin cytochemistry and actin staining for usefulness as quantitative markers of muscle capillaries and 2) to describe the ontogeny of capillary density changes in developing porcine muscle. Muscle samples were obtained from three to eight crossbred pigs at each of the following ages: newborn, 1 to 2 d and 1, 2, 3, 4.5 and 24 wk. Cryostat sections were stained or reacted for alkaline and neutral phosphatase, dehydrogenase, actin, a panel of nine plant lectins (fluorescein isothiocyanate conjugated) and routine cytochemical tests for muscle fiber typing. Capillaries were quantitatively marked by reactions for dehydrogenase activity in the young pigs but not in the oldest animals. The lectins, soybean agglutinin, Bauhinia purpuria agglutinin, Ulex europeus agglutinin-I and Griffonia simplicifolia agglutinin-I (GS-I) quantitatively stained capillaries at all ages. Histological observations of thin sections of epon-embedded tissues served to validate the lectin and cytochemical capillary staining. Micrographs of sections stained with the lectin GS-I were used to count capillaries and muscle fibers so the capillary:fiber ratio (C/F) could be calculated. Deep (red) and superficial (white) aspects of muscle sections had different C/F at birth, 2, 4 and 24 wk. The deep aspects (DA) had higher C/F than superficial (SA) aspects (at all four ages), and there were age-dependent increases (P less than .001) in C/F of DA and SA. This study demonstrates the usefulness of lectin staining for determining C/F in porcine muscle.