Effect of needle puncture and intradermal fluid injection on epidermal cell kinetics of albino guinea-pig skin.

The flanks of male albino guinea pigs were used to study the effect of needle puncture with or without intradermal (id) injection of 0.1 ml fluid. The center of the raised bleb was marked and biopsies taken 1,4,8,24,50 and 72 hrs after needle puncture and 1 hr after intraperitoneal (ip) injection of tritiated thymidine (3H-TdR). There were no significant differences in labeling index (LI) or mitotic index (MI) 1 hr after id, ip, or subcutaneous (sc) injection nor in percent labeled mitoses, 7 hrs after id or ip injection. The earliest increase in LI (180% above control) occurred 12 hrs after needle puncture, peaked at 24 hrs (ca. 3X control), and returned to control level by 50 hrs. The area affected had a radius of about 5 mm from the point of needle entry or center of the bleb. Within 12 hrs after needle puncture, there was an increase in labeled cells primarily at the periphery of the bleb area, about 4 mm from the point of needle entry. By 24 hrs, the distribution of labeled cells had moved toward the bleb center (LI = 65%). The first increase in mitoses (MI = 2.5%) was seen 24 hrs after needle puncture. It is concluded that id injection introduces no significant error in LI or MI to 8 hrs after needle puncture. It does, however, trigger many noncycling basal cells into DNA synthesis after 8 hrs, and this may increase the rate of transit of these cells to the granular layer.