Rp. Smith et al., ASYMMETRIC INTERACTIONS BETWEEN PHOSPHORYLATION PATHWAYS REGULATING CILIARY BEAT FREQUENCY IN HUMAN NASAL RESPIRATORY EPITHELIUM IN-VITRO, Journal of physiology, 496(3), 1996, pp. 883-889
1. The effects of the sequential stimulation of ciliary beat frequency
(CBF) via two different phosphorylation cascades (dependent on protei
n kinase A (PKA) and calmodulin, respectively) were determined using v
ideo microscopy applied to a perfused preparation of human nasal respi
ratory epithelium in vitro. Dibutyryl cyclic AMP (db-cAMP) (10(-3) M)
was used to stimulate PKA and the calcium ionophore 4-Br-A23187 (10(-5
) M) was used to stimulate calmodulin-dependent phosphorylation. 2. Pe
rfusion with db-cAMP (10(-3) M) alone showed an early rise in CBF (15.
0 +/- 4%, mean +/- S.E.M., P < 0.05) by 10 min which remained elevated
for 35 min; in contrast, the highest CBF response to 4-Br-A23187 (10(
-5) M) alone was not achieved until 35 min (16.1 +/- 1.8%, P < 0.05).
3. When a db-cAMP stimulus was applied to cells which had been pre-inc
ubated with 4-Br-A23187 for 30 min, a further rise in CBF (maximal at
20 min, 14.3 +/- 2%, P < 0.05) was observed. Reversing the sequence of
perfusions, cells pre-incubated with db-cAMP showed no further rise i
n response to stimulation with 4-Br-A23187. 4. We hypothesized that PK
A inhibited the response to the 4-Br-A23187. This notion was supported
by the restoration of the CBF response (22.8 +/- 4%, P < 0.05) to 4-B
r-A23187 when the cells were pre-incubated with the protein kinase inh
ibitor 1-(5-isoquinolinyl-sulphonyl)-2-methylpiperazine (10(-3) M), be
fore the sequential perfusions with db-cAMP and 4-Br-A23187. We conclu
de that the A23187-dependent pathway, which regulates intrinsic CBF, i
s inhibited by db-cAMP but not vice versa.