Spontaneous activity in isolated bovine mesenteric lymphatics.

1. Longitudinal tension was measured in isolated segments (approximately 20 mm in length and 2 mm in diameter) of bovine mesenteric lymphatic vessels.2. Seventeen out of thirty-nine vessels showed regular spontaneous rhythmic contractions, the most common frequency being about 2/min.3. The strength of each contraction was related to the duration of the preceding pause, a longer pause being associated with a stronger contraction.4. Noradrenaline increased the frequency and decreased the amplitude of the contractions. This effect was abolished by alpha-receptor blockade with phentolamine.5. Isoprenaline slowed the frequency of the contractions. This effect was abolished by beta-receptor blockade with propranolol.6. Acetylcholine had little effect on the rate of spontaneous contractions.