A One-Way Track for A.P. Indy : Horse racing: $2.9 million colt makes his long-awaited Triple Crown debut in the Belmont Stakes.

If A.P. Indy runs as expected in the 124th Belmont Stakes, owner Tomonori Tsurumaki will win the race that traditionally has been dominated by the old guard of American’s racing and breeding establishment.

The Japanese land developer has been buying horses at major U.S. auctions since the mid-1980s, and he was especially prominent at the Keeneland Yearling Sales in 1990. He spent $2.9 million for a son of Seattle Slew, named him A.P. Indy after the Auto Polis leisure center that he owns in Japan, and put him under the care of one of America’s best trainers, Neil Drysdale.

Tsurumaki’s investment was rewarded as A.P. Indy developed into one of the best horses of his generation, and he will be favored at Belmont Park Saturday. This is a hardly an unusual phenomenon, of course. If Japanese investors can buy such institutions as Rockefeller Center, Pebble Beach and Columbia Pictures, there’s no reason they can’t annex the third leg of the Triple Crown too.

Yet here is an aspect of the Japanese success that is disquietingly familiar. If an American horse owner wanted to do what Tsurumaki has done -- invest his money and try to win a race such as the Japanese Derby -- he wouldn’t be able to do so. He couldn’t even get his foot in the door. Of Japan’s many well-publicized obstacles to free and fair trade, few are more blatantly restrictive than the rules that govern the horse racing industry.

To race horses in Japan, an owner must belong to the Japan Racing Association, a subsidiary of the country’s Ministry of Agriculture, Forestry and Fisheries. It is comparable in some ways to the patrician Jockey Club in the United States, and it has been impenetrable for outsiders. As a result, foreigners cannot own race-horses in Japan, although a few do run horses under the name of a Japanese “associate.” This is not merely an anti-American position. Even the most prominent horse owner in the world, multibillionaire Sheikh Mohammed al Maktoum of Dubai, hasn’t cracked the JRA.

However, the restrictions that Americans in the racing industry find most galling are the ones that Japan places upon on foreign-bred horses. Once a horse has raced abroad, he may not compete in Japan. (The sole exceptions are the invitational Japan Cup and one prep race that precedes it.) An unraced foreign-bred horse may enter the country upon payment of a $30,000 duty, but he will be eligible for only about one-third of the country’s races and he would not be permitted to run in Japan’s 3-year-old classics.

This is not a distinctively Japanese type of restriction, by any means. Countries with relatively weak breeding industries often try to protect their major races from domination by invaders. Canada’s Triple Crown, similarly, is open only to horses foaled north of the border.

The horse industry is one economic arena where America leads the world while Japan has been a laggard. The economic journal Nihon Keizai Shimbun acknowledged the “poor genetic base” and “low performance of domestic racing horses,” and blamed the deficiencies on “the quality of the stallions imported in the past.” The Japanese invitee to the Washington, D.C. International was inevitably a laughingstock last-place finisher.

In recent years, foreign domination of the Japan Cup has further underscored the weakness of the home forces. But Japan is making efforts to catch up, and its restrictive rules governing the importation of foreign racehorses don’t apply to breeding stock. Japanese buyers have acquired such important stallion prospects as Sunday Silence, the 1989 horse of the year, and Scan, one of the top American 3-year-olds of last season. It takes generations to develop a mature breeding industry, but Japan is approaching this goal with characteristic planning and protectionism.

Sen. Mitch McConnell, R-Ky., has been one of the most outspoken critics of Japan’s policies. His constituents in the bluegrass country would love to sell more racing prospects to Japan, and last fall McConnell urged Carla Hills, the U.S. trade representative, to make thoroughbreds an issue in trade talks between the countries.

U.S. negotiators raised the subject among the dozens of issues that were discussed at a trade meeting in Hawaii last December, criticizing the “exorbitant” duty on imported horses and urging that the JRA open more races to foreign-bred runners. The Japanese representatives were largely noncommital at the time, but the JRA has proposed to liberalize the opportunities for foreign-bred runners.

That idea has encountered stiff opposition from the country’s breeders. The barriers against foreign owners may eventually be eased too.

But any progress is sure to be slow and deliberate, while the Japanese have unfettered access to the American racing industry. When Tsurumaki’s horse competes at Belmont Saturday, he will be running over what is tantamount to a one-way street.