Commerce Secretary Frederick Dent revealed Wednesday that he and Secretary of State Henry A. Kissinger have been discussing whether U.S. business firms will be allowed to participate in a Moscow exhibition of police equipment. Dent said a decision will be made soon on the advisability of exporting such items as personal surveillance, observation and information-gathering devices. Sen, Henry M. Jackson (D.Wash.) had earlier declared he was outraged by U.S. participation in the Moscow exhibit Aug. 14. He said he would ask the Senate subcommittee he heads to look into the matter.