Table 2.

Effect of long-term PGE₂ treatment on the inhibitory activities of cAMP-elevating compounds

	% Inhibition
	Control	PGE2-treated
PGE2 (10−5 M)	45±6	21±5*
Formoterol (10−6 M)	42±5	41±7
Forskolin (10−5 M)	80±6	85±3
IBMX (3 × 10−4 M)	59±8	67±4
Bu2-cAMP (10−3 M)	48±5	44±7

Mast cells were incubated (24 h) without (control) or with PGE₂ (10⁻⁵ M) and then washed extensively. The cells were then incubated with a cAMP-elevating compound for 10 min before challenge with anti-IgE (1 : 300) for a further 25 min for histamine release. Values are expressed as the percentage inhibition of the control histamine releases and these were 39±7 (control) and 34±8% (PGE₂-treated). Values are means±s.e.m. for five experiments. Asterisk denotes a significantly different (P<0.01) level of inhibition following PGE₂ treatment compared to control.