Temporal dissociation in the ability of ouabain and furosemide to inhibit K+-transport in rat submandibular salivary gland slices at various postnatal ages.

Slices of glands from 1, 7, 14 and 21-day-old rats were perfused with a physiological salt solution in a lucite chamber; acetylcholine-induced release and uptake of K were compared to that of adult glands, in the absence and presence of the ion-transport inhibitors, ouabain and furosemide. Without inhibitors, peak K efflux from the glands of 1-day-old rats was 50 per cent of that in 7, 14 and 21-day-old rats, and 33 per cent of that in adults. Maximum K+ uptake was 72 per cent of that in 7, 14 and 21-day-old rats and 61 per cent of that in adults. However, K+ uptake was a larger part (78 per cent) of the preceding efflux in glands of 1-day-old rats than in adult glands (43 per cent) or in glands of 7, 14 and 21-day-old rats (55 per cent). Ouabain (10(-3) M) immediately after a 3-min pulse stimulation with 10(-5) M acetylcholine abolished K uptake at all ages. Furosemide (10(-3) M) inhibited K uptake throughout but its effect increased with age. Thus K+ uptake was 21 per cent less than in the absence of inhibitor in slices from 1-day-old rats but 73 per cent less in adult glands. Similar, but smaller, effects were observed when exposure to furosemide followed acetylcholine. Both K efflux and uptake can thus be elicited in rat submandibular glands from the first day of life and the increased response with age correlates with morphological development and with the progressive, postnatal appearance of acinar cell. The large uptake:efflux ratio suggests that a Na, K pump, responsible for a large portion of K+ uptake, is already present and active in the glands of 1-day-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)